There are 12 playable characters in Super Smash Brothers; eight that are available at the start, and four that can be unlocked in single player mode through completion of certain challenges. They all have certain advantages and disadvantages, and although this game is very well balanced, certain characters are better than others are. However, Super Smash Brothers 64 character tiers are very subjective, so characters will not be listed in order from best to worst. I give a basic summary of characters, and go can go to the in-depth guides for more specific info, but you will have to figure out character rankings for yourself.
Captain Falcon
Probably one of the most dominating players in the game, Captain Falcon's greatest assets are his speed, his backwards throw, and his fire kick. His Falcon Punch, while powerful and certainly effective in certain situations (notably, immediately after being given a new life and while still invincible for a couple of seconds), should not be relied upon too heavily because it requires about two seconds to charge up during which time Falcon is vulnerable to any number of attacks from opponents. The Falcon Kick useful move (note that it is not nearly as powerful as the Falcon Punch) because with it you can attack a player from a distance (i.e., the move glides Falcon across the board). The Falcon Kick is particularly effective if used when an opponent is already off the board (i.e., Do a Falcon Kick off the edge, hit the opponent, and jump back - Falcon can make it). The Fire Kick (Falcon's Forward + A) is also a devastating weapon, but, again, be prudent when using it because it is a slightly slower move than, say, Link's Forward + A move. The Fire Kick should be used primarily to finish players off once they are off the edge and jumping back. Finally, Falcon's throw, particularly his reverse throw (R + Joystick away from the opponent) is probably his most useful attribute. For one, players are defenseless against the grab (a shield does not block it). Moreover, it can be used to clear out a brawl. Falcon's greatest strengths, unlike Link's, do not lend themselves to melees, so it is generally in Falcon's best interest to throw players away from one another and then isolate. Falcon's speed enables him to run quickly up to players, grab them, and then throw them before they can defend themselves. When near an edge, using the reverse throw to launch players off the board is an effective strategy, too.
Donkey Kong
The large primate from the old arcade-style Mario games is back again. This time he's larger and better than ever. He is the hardest character to K.O., because of his size. Some can go on until 300% damage using him. Donkey Kong is a mix of endurance and power. He has rather mediocre spped, but his power makes up for the loss. His main B button attack, the Giant Punch takes around 3-4 seconds to charge (In mid-air or on the ground) just don't let him get hit, or he'll have to start over again. His (Up+B) attack, the Spinning Kong is used for getting back up on the stage after your two jumps. The Spinning Kong is a horizontal move, meaning it will get you little or no air. This move lets Donkey Kong imitate a helicopter and literally spin for a short amount of time. Finally, his Hand Slap/Ground Pound is by Down+B. This little move is a killer when you use it in the Mushroom Kingdom (Classic Mario World) level (In the Bottom Left Area, where there's a ceiling), or Hyrule Castle's little greenish building on the right side of the stadium. This move will get all enemy characters that are standing on the ground into the air. Because of the two spots in the two levels that I have mentioned above, the Hand Slap move will cause opponents to go up, hit the ceiling and fall down again... *Repeat Many Times... *Cough *Cough.... Also, the Z+A (throwing move) will let you pick up an opponent and simply toss them. You can also walk with them on your back. (Try jumping off the stage with your enemies on your back) A special little thing about Donkey Kong is his ability to move with crates or barrels. However, he can only jump once when his is holding these objects.
Fox
Fox McCloud is the protagonist in Nintendo's futuristic Starfox fighter-plane games. Although you never saw his character in action (only his ship), his special moves in Super Smash Brothers are gracefully taken from his ship's maneuvers. He is a fast, somewhat light character with some powerful moves.
Some notes with Fox:
(Up+B) - Fox's recovery can be aimed. After initiating the 'charge', push the direction you want him to fly. This allows explosive moves towards where the action is.
(Down+B) - Fox's shield can deflect most projectiles, making him the natural enemy of Samus and Link, as well as any thrown object. Most of these objects are returned towards the thrower able to do quite a bit of damage to them.
Throw - Fox is an excellent thrower, he has a quick grab and long range throw. This can easily become the basis of your strategy with him, hug the edges and grab recoverers to quickly hurl them off again.
Aerial Attacks - Fox flies a Starfighter, naturally he's at home in the air. A pretty effective jumper with an array of powerful air executed attacks and kicks. When not throwing, Fox should be in the air, keeping him air borne keeps him where he's strongest.
Juggle - Fox can quickly execute (Up+A) attacks while in the air to knock other aeriel enemies upward, then land and quickly launch the same attack. Using this method, one can keep an enemy in the air, doing consistent damage to her until her percentage is high enough to launch them laterally. Alternatively, the juggle is strong enough to throw them so high they get a KO.
Speed - Fox is one of the fastest characters to play; using this in combination with his Aerial attacks is very effective to keep your enemy guessing and off guard. Fox is able to make quick hits in and then make getaways just as quickly when heavier fighters retort, allowing him to get into the air to make another aerial attack. In addition, his speed is half of what makes him such an effective thrower.
Jigglypuff
Kirby
Link
His speed is slow, and he has the worst jumps in the game but he is very powerful. Pressing Up+B while in the air causes him to spin his sword around, making him go higher. Link has a good arsenal of weapons. He is able to throw a boomerang, and bombs. But bombs are on a timer, so don't be cought holding them when they explode, as the blast radius also damages you.
Luigi
Mario
When one thinks "Nintendo", this guy comes to mind. A plumber with a moustache and a penchant for jumping who happens to be in love with a perpetually kidnapped princess (I mean, what the heck, Nintendo?), he and his games fill many of the spots for top-selling games of all time. In Super Smash Brothers 64, this red-capped and blue-overall wearing Italian is a good all-around character. He has fantastic aerial recovery time, a great u-air juggle, and very annoying fireballs, but isn't quick enough to keep up with the likes of Fox or Captain Falcon.
Ness
Ness is a young psychic boy (exact age unknown), protagonist from Nintendo's Earthbound RPG series. Ness is a hidden character, so you will have to unlock to use him in versus play. To do this, you have to beat the game on Normal difficulty with 3 stock, no continues, and then defeat him in 1v1 combat. He is probably one of the more difficult characters to play with, since his third jump is very tricky to pull off for a new player, and his floaty, circular second jump can weird out even veteran players. He is a fairly light, slow character with powerful attacks, and is the only character with a healing move.
Pikachu
An electric Pokémon from the game series of the same name, Pikachu is very powerful and agile. He is so powerful and agile, in fact, that he has been considered "cheap" by the unenlightened. I myself find few disadvantages to the little guy, but then again, he's my main. He has one of the best recoveries, if not the best, in the game and has a simply unavoidable edgeguard. He suffers from short range on the ground, is relatively light, and takes a good level of skill to play well, but this electric rat could very well be your route to victory.
Samus
Samus is a master of distance, but an all around good character to play. Various moves need to be mastered to be an effective Samus player.
Bomb Recovery : This is not so effective when recovering from a low position off the platforms, but when knocked far to the side Samus can easily recover from distances most other characters wouldn't dream of. Using Samus' Bomb attack(Down+B) and pushing the direction you want to go, Samus will roll into a ball and drop a bomb - but she will remain lateral, not falling further while rolling. After the bomb attack she will return to normal form and begin falling again, which is when you can initiate another bomb attack. In this method, Samus can slowly but surely move back towards the platforms, using her final (Up+B) recovery to get back on the platform if she needs. A strength of this particular tactic is that, if high enough, it gives some flexibility in returning to the side platforms. Samus could recover up(Up+B), drop further bombs and land on the platforms, drop fast to grab the edge, or come back with another attack.
Spike : (Down+A) While jumping, do an A attack down, Samus should do a quick spin kick towards the ground. Timing is crucial when doing a Spike(Which can be done with other Characters, but not all of them), but when you have knocked an enemy off the side, jumping out to meet them while they are still not over the platform, then executing a Down+A attack, will send them quickly towards the ground with very little chance of recovery. This attack can easily KO low precentages, as long as they are knocked off.
Charge Shot : Pressing and holding B will charge up a shot, but you can also interrupt this charge and do other things. What does this mean? Every spare chance you have, you should be charging. Enemies must always be wary that you have a fully charged shot, that can do upward of 25% damage and send them flying. This will not only obviously make them more cautious towards you, letting you take the initiative but also gives you a ranged attack to send at them when they least expect it. Do not make the obvious mistake of simply lobbing projectiles from the far side of the map hoping to hit someone randomly. First off, an uncharged shot is good for little more than annoyance in most cases. So you should only attack with a charged shot. Secondly, you must look at your enemies current tactical positions - are they recovering, which direction are they moving, etc. Shoot when you are almost guaranteed to land a hit, when they are in the air recovering, attacking someone else, or otherwise preoccupied mentally or physically. If they see it coming, but their character is simply in no position to move out of the way, fire. There is no reason that the attack MUST be ranged, a charged shot could be a perfect end to a melee combo, or it can be fired at relatively short distances at a charging enemy. Further uses of the charge shot include using excellent timing to hit an enemy that is recovering from the edge. If an enemy is already off the edge, recovering, a charged shot USUALLY is enough to send them out for good. Charged or uncharged shots are also good for getting the last damage in on an enemy, ensuring that the kill is yours(Whether you actually earned it or not.)
There are some other notes to take with Samus.
Grapple - Samus's throw is pretty dismal, and the range is more of an impedement than an asset. Do not attempt to get into throw fests with other characters unless you are sure you know what you are doing. When Samus misses her grab, she is vunerable to ANYTHING for quite some time as her grapple comes back in. This aside, the grapple does have a range advantage, and can be used to pull one enemy from another melee for free damage, or hit a charging enemy off gaurd. At maximum range, the grapple also can just barely grab a Hammer weilding enemy for a throw, but this is tricky to pull off.
Ground Juggle - Like all characters who can spike, Samus can also juggle towards the ground, using ground attacks to keep an enemy pinned while she racks up damage.
Smash-A - Samus's smash punch is pretty powerful, but also reasonably quickly executed and should definatly make up the brunt of your melee combos.
Back-A - Samus's back jump kick, pressing and attacking in the direction opposite of which she's facing, is also reasonably powerful and can easily send enemies off the edge in an ariel bout.