One against one, and one against the crowd. Ninja Assault and X-Fightingpet are the traditional kind, trading blows along a single line. BioGems is the odd one out and fights its battles on a match-three grid. Da Vinci's Flying Robots sends renaissance machinery at you instead of fighters. Short matches, so a loss costs a minute at most.
44 games, free to play in the browser.
These run on their own, without Flash — all 150 of them.