Huh...
...
Hmm...
...
Damn you!
...
oh, screw it.
S.L.A.I.
It's fun, witty, creates a believable game world, is rooted in reality yet is still a solid sci-fi, has an interesting story, fun mechanics, great customization, semi-believable characters (they all use aliases, which are honestly pretty bad...), and is over all a fun mech shoot em-up.
Making it a sport throws an interesting wrench in the system, but it is still built and lives off of it's shooter elements, and it fits a variety of play style. be it strafing and shooting, or a stealthy sniper, or a vile opportunist.
Personally, I had a light, high flying, super fast, invisible ninja mech with a super laser cannon, triple-missile launcher, giant machine gun, and seven foot long chainsaw.
And I had a samuri of a polar bear on a computer chip helping me. With a pompous British wolf.
Good times.
There all other shooters, but this is the one I remember the most.
(dusts off PS2, puts in S.L.A.I, becomes separated from the world for the next five hours)