Best. Minigame. Ever.

a_rabite (?), Jump Forever, there's a reason you can move left and right, is that after 100 jumps, the people with the ropes will move to the left and right of the screen and you'll have to try to stay center. all this, while the speed of each jump changes randomly from fast to superfast to super slow. I know this because I used to play this minigame all the freaking time.

I seriously enjoy ballista in FFXI (the MMO). I consider this a mini-game based on the fact that you have to decide to play it :P it's basically PvP but with a little more to it than kicking the other guy's ass. You're basically split into two teams usually by region, and the idea is to dig in the ground to find petras, and toss them in a rook that changes location every few minutes. You can organize with other people to protect certain rooks from the other team, or try to overtake the other rook, etc. You can dig up various temporary items too that help out. (I found several giant's potions in one game, which boosted my max hp to 2500). The team with the highest petras tossed in the rook wins. It's a load of fun.

I dunno if it's considered a mini-game, but the Gummi Ship stages in Kingdom Hearts II are a load of fun. They look awesome, and there are a lot more bullets flying at you this time around XD. It's also neat to build your own gummi ship completely from scratch (being able to curve and bevel pieces placed on the grid is extremely neat and has led to a few nice designs)

I can't think of too many at the moment. This'll have to do :P

Jam it back in, in the dark.