Ninja Gaiden.
Man, sorry to sound like a sugar-filled 12yr old, but this game is sooooooooooo cool!
It's like the designers said [official Team Ninja meeting minutes] 'lets have a game with ninjas and commandos and tanks and guns and monsters and loads of other wicked shit! Then we'll have everyone EXPLODE when they die!!! Yeah, man, that sounds AWESOME!!!!'. [/official Team Ninja meeting minutes]
Seriously, this game is lots of fun. Extremely camp, but lots of fun.