Killer7

FPS puzzle game from Capcom. Played on Nintendo Gamecube, also available on pS2.
SUDA 51's game before No More Heroes, and possibly the weirdest game you will ever play. It's an on-rails shooter-puzzle-adventure... or something like that. You play as a team of 7 hitmen in one, all with unique abilities, as youfight the Heaven Smiles, exploding zombies. It's really very tricky to summarise, as the unique narrative is one of the game's strongest points.
The graphics are really quite special, with a very original gritty cel shaded style; it's certainly not a kid's game, with extreme amounts of blood and very mature themes. Gameplay involves running along set paths, stopping to scan for enemies, then hitting enemies' weak spots, and solving puzzles. It seems like little on the surface but the game has to be judged as more than the sum of its parts.
I give it 9/10. It's difficult to describe, but suffice to say, there's nothing else quite like it.