Super Smash Bros. Brawl/Unlockables

Secret Characters
Complete one of the objectives for each character, not all 3 are necessary. All characters can also be unlocked in the Subspace Emmisary and Brawl Mode. If you unlock them in Brawl mode the winner fights the secret character.

Ness

 * Play 5 matches in Brawl mode, then defeat him in battle.
 * Reflect ten projectiles, then defeat him in battle.
 * Complete Stage 29 of the Subspace Emissary and Ness will join your party.
 * The best way to unlock Ness is play the 5 matches.

Marth

 * Play 10 matches in Brawl mode, then defeat him in battle.
 * Finish Classic mode on any difficulty level, then defeat him in battle.
 * Complete Stage 8 of the Subspace Emissary and Marth will join your party.
 * The best way to unlock Marth is to go to Stage 8 of the Subspace Emissary. Plus you view a awesome cutscene with Meta Knight and Marth.

Luigi

 * Play 22 matches in Brawl mode, then defeat him in battle.
 * Beat Classic on any difficulty with no continues, then defeat him in battle.
 * Complete Stage 29 of the Subspace Emissary and Luigi will join your party.
 * The best way to unlock him is probably to either:
 * Play the 22 Brawl matches or:
 * Go on an easy difficulty for you and sweep through without using continues. Your choice.

Falco

 * Play 50 matches in Brawl mode, then defeat him in battle.
 * Beat 100-Man Brawl, then defeat him in battle.
 * Complete Stage 18 of the Subspace Emissary and Falco will join your party.
 * I would play the 50 matches, or, if you want to take a quick skill test, complete the 100 man brawl.

Captain Falcon

 * Play 70 matches in Brawl mode, then defeat him in battle.
 * Beat Classic Mode in under 12 minutes on at least Normal difficulty, then defeat him in battle.
 * Complete Stage 20 of the Subspace Emissary and Captain Falcon will join your party.
 * The sheer easiest way to unlock Mr. Falcon himself is to go through classic mode.

Lucario

 * Play 100 matches in Brawl mode, then defeat him in battle.
 * Beat all 5 difficulties on Target Smash, then defeat him in battle.
 * Complete Stage 21 of the Subspace Emissary and Lucario will join your party.
 * The best way to unlock Lucario is to beat all 5 difficulties on Target Smash. You have 2 minutes to break 10 targets. Come on.

Snake

 * Play 130 matches in Brawl mode, then defeat him in battle.
 * Play 15 matches on Shadow Moses Island stage, then defeat him in battle.
 * Complete Stage 23 of the Subspace Emissary and Solid Snake will join your party.
 * The best way to unlock Snake is to probably just play 15 Brawl matches on Shadow Moses Island. All you really have to do is set the computers on Lv. 1, 1 stock, and just smash attack the life outta them. X3

R.O.B.

 * Play 160 matches in Brawl mode, then defeat him in battle.
 * Collect 250 trophies, then defeat him in battle.
 * Complete Stage 27 of the Subspace Emissary and R.O.B. will join your party.
 * I would either play 160 matches in Brawl Mode or go to Stage 27 (the plot twist) in the Subspace Emissary. 250 Trophies would take a bit long, and you could get many duplicates.

Ganondorf

 * Play 200 matches in Brawl mode, then defeat him in battle.
 * Beat Classic Mode on Hard difficulty with Link or Zelda, then defeat him in battle.
 * Rescue Link and Zelda in Stage 30 of the Subspace Emissary, complete the stage, and Ganondorf will join your party.
 * I would beat Classic Mode with Link or Zelda. All you really have to do is just beat 11 stages, plus a boss, to get Ganondorf.

Mr. Game & Watch

 * Play 250 matches in Brawl mode, then defeat him in battle.
 * Beat Target Smash with 30 characters on any one difficulty level, then defeat him in battle.
 * Mr. Game & Watch will join you when you defeat the boss Duon in part 25 of the Subspace Emissary.
 * Game & Watch is probably one of the last characters you unlock via Target Smash. I would beat Duon, go to Stage 25, and not have to do a battle. Win-win?

Sonic

 * Play 300 matches in Brawl mode, then defeat him in battle.
 * Beat Classic Mode on any difficulty with 10 characters, then defeat him in battle.
 * Play over 10 hours in Brawl mode.
 * Complete Stage 31 of the Subspace Emissary, and Sonic will join your party.
 * I would either go to Stage 31 of the Subspace Emissary to activate a really awesome cutsecne, play 10+ hours in brawl mode (just leave 2 human controllers out all night), or beat classic mode with 10 characters. Good character comes easy.

Jigglypuff

 * Play 350 matches in Brawl mode, then beat it in a match.
 * Complete the Subspace Emissary, then return to Stage 18. At the end of the level where you must shoot yourself through barrels, stop on the platform below the new door. Go in and beat Jigglypuff.
 * Complete the Subspace Emissary, then complete twenty single-player Events on any difficulty and beat it in a fight.
 * Do the 20 events. They are easy to do, and you can always just do them on easy.

Toon Link

 * Play 400 matches in Brawl mode, then defeat him in battle.
 * After completing Subspace Emissary, finish Classic mode with any character on any difficulty, then defeat him in battle.
 * Complete the Subspace Emissary, then return to Stage 9. At the beginning of the level after the first mini-battle with Primids, a new door appears. Go in and beat Toon Link, then finish the stage.
 * I would complete the Subspace Emissary, beat classic mode with any character, then go and unlock Toon Link. This is very easy to do (not the Subspace Part, but classic mode) and you will get Toon Link easy.

Wolf

 * Play 450 matches in Brawl mode, then defeat him in battle.
 * Beat Boss Battles mode with Fox or Falco, then defeat him in battle.
 * Complete the Subspace Emissary, then return to Stage 14. At the end of the second part of the level, go to the bottom of the elevator shaft instead of going into the door and into the new door that appears there, near the giant Bryans. Beat Wolf, then finish the stage.
 * The best way to get Wolf is to unlock him in the Subspace Emissary.

Music
Information about unlockable music can be found here.