Super Smash Bros. Brawl/Multi-Man Brawl

The Multi-Man Brawl gives you 6 different battle modes:
 * 1) 10-Man Brawl (battle against 10 enemies).
 * 2) 100-Man Brawl (battle against 100 enemies).
 * 3) 3-Minute Brawl (try to survive for 3 minutes).
 * 4) 15-Minute Brawl (try to survive for 15 minutes).
 * 5) Endless Brawl (battle against unlimited enemies until you quit or you are defeated).
 * 6) Cruel Brawl (battle against very difficult enemies).

In this game, the enemies you're battling against will be the Fighting Alloy Team. The main four come in different colors and sizes that mimic normal characters: Hint: You don't actually need to KO them; they just need to fall off the stage in order for it to count, be it friendly fire from another CPU or just the odd occurrence of them jumping off the stage.
 * 1) The Red Alloy: similar to Captain Falcon.
 * 2) The Blue Alloy: similar to Zelda.
 * 3) The Yellow Alloy: similar to Mario.
 * 4) The Green Alloy: similar to Kirby.
 * 5) Also, sometimes a normal playable character will show up. One is randomly thrown in with every 25 or 30 alloys. In 10-Man Brawl, the final enemy will be a copy of your own character.  Note that these are more efficient and durable fighters than the alloys.

100-Man Brawl
This challenge doesn't seem very hard at first because all the enemies can be killed with a well-placed smash, but once you get to less than 25 alloys left, it becomes a real challenge.

The beam sword is a very effective item in 100-Man Brawl because of it's long range and powerful smash attack. Pokéballs and Assist Trophies are also very useful, unless you get a Pokémon like Goldeen, or Assist Trophies like Nintendogs or Resetti. Fans are also excellent choices, but work better if thrown; enemies pop straight up into the air at high speeds, even if it's the last 25 — stand under the left or right platform and throw it straight up, then watch as the Alloys fly off-screen the second they step off their platforms. Another very good item to use is the bumper — stand below the right or left platform and throw it straight up, and it will get stuck right where alloys spawn, creating instant kills very easily.

Beating this with every character yields a Blue Alloy trophy; there are also prizes for beating it in less than four minutes and less than three minutes and thirty seconds.

15 Minute Brawl
If you use two Lucario's, you set up your characters to charge their shot in a way that juggles the enemy for extremely long periods of time. Simply have one Lucario charge up its energy, then have the other move on top of him but face the other direction and charge up its energy. The crossing paths will juggle the enemies between the two directions. You'll still need to watch the game in case bomb-ombs appear, but you shouldn't have to do much other work than reset the dual charge stance.
 * Using Lucario Co-op