Super Smash Bros. Melee/Ness

Summary
Ness, despite being a low-tier character, has massive potential. He is one of the trickiest characters in the game. He has a few very powerful moves. The thing that really holds players back is his steep learning curve. Ness is a great character for those who want to work hard and surpass high-tier players with a low-tier character.

Pros

 * Extremely tricky
 * A few extremely powerful moves (i.e. bat, bair, PK Flash) considering his small stature
 * Often unexpected (not many people play a good Ness)
 * Multiple projectile attacks
 * Plays a great aerial game
 * High priority

Cons

 * Very difficult to master
 * Recovery with up + B is initially difficult for beginners

Baseball bat (Smash Forward + A) + PK Cross (B)
If you play one on one, this is an invaluable technique. While somewhat near the edge of a stage, use a baseball bat to knock the other player of the edge. While he trying to get back, start holding down B. This will start Ness's PK Cross. Hold the analog stick in the direction of the edge so that when the green ball reaches the apex above Ness, it will start to go down towards edge of the stage. Time the move so that by the time your opponent comes back to the stage, the green ball is at full power. (The amount of time is different depending on your opponent: for instance, Kirby will take longer to get back to the stage then Gannendorf.) Release B to deal maximum damage just as your opponent tries to climb to the stage. Because it's at full power, this move almost surely knock out any opponent over 50% damage.
 * It is also possible to have the PK Cross ball come back toward Ness. This way, when your opponent tries to come back and attack you, they will be attacked instead.
 * Usually you want to stand near the edge to perform this move. You can have the PK Cross ball come back toward Ness, and at the same time it's going toward the edge. This way, if you time it wrong, the player won't be able to attack you since they would get hit by the PK Cross if they did.
 * You don't need to use the baseball bat. Any move that throws another player over the side of the stage far enough will work. Using the Back Throw works the best (esp. at higher damages). Block often, so when your opponent gets near the edge of the stage, perform a roll to the edge to get closer to the edge than them. Then, use a back throw to throw them over the edge. A back throw is actually more likely than a forward throw to throw the player completely offscreen for a K.O. at higher damages (100% or greater).

Headbutt (Aerial Up + A) + PK Thunder (B Up)
Doing this move requires a firm command of Ness's PK Thunder to aim it where you want it to take you. Once you have an opponent trapped in a barrage of headbutts preventing him from landing on the stage, you can pull this off. First the opponent needs to have around 80% or more so that the attack will be lethal. Do one more headbutt and as soon as you do, take out your PK Thunder and aim in a direction where your opponent will fall. It's tricky at first, but try to predict where he will be when you hit yourself with it to attack him head on.

PK Inferno (Grab + Down) + Home-Run Swing (Smash Forward)
A very simple combo to pull off, you simply use PK Inferno on your opponent and use your smash on him while he's on fire. If the opponent DI's horizontally away from you after you use the PK Inferno, PK Shove him instead. If he DI's up, use your Headbutt (Aerial Up + A) on him.