it can be any character from any game and yo ucan list your top 3

1. illidan stormrage - warcraft 3, world of warcraft i like him cos of his voice actor and cos hes just badass
2. raiden MGS2,rising,MGS4, ive always liked raiden cos he's like a reincarnation of grey fox but not as cool as grey fox
3. dante from the old dmc games, dnt like the new dante looks like a twat old dante was bad ass

Easy

Boo, the Miniature Giant Space Hamster!
It's not a playable character... it would make the game way too easy.

Best character in the game.

I love Scorch from Republic Commando. He's a pyromaniac, loves explosives and whatnot, and he's totally badass.

And he's got a sense of humor.

Halo. He's a pretty cool guy.

I think it would have to be a villain. SHODAN, perhaps.

Edit: I forgot the why part. Well, she's got visual flair, and she makes the game (System Shock, obviously) quite a bit more interesting than it would have been without her. Not that it wouldn't have been brilliant anyway. And Brosius' voice acting behind the modulations couldn't be more perfect.

Tommy Vercetti. He's just so fed up with everyone's bullshit.

Samus Aran, but void the blond barbie.

Secondarily, the Hylian Hero, Link.

I like Raziel from the Legacy of Kain series.
Honestly, it's just because he looks and sounds cool as hell!

… And no, I am not a edgy teenager ...

Easy, Grom Hellscream!

He's possibly the strongest WC3 hero (except perhaps for Arthas with Frostmourne / Illidan's demon form) and of course because of the badass cinematic

Edit, or perhaps Gabriel Angelos because of his awesome voice and quotes

Sister Miriam Godwinson from Alpha Centauri; what a sweet and lovable lady.

Classic gaming - Duke Nukem. Badass tough guy. Tons of great one-liners. Chicks love him. Wonderful attitude towards life. Huge weapon arsenal. Hates alien invasions.

Modern gaming - Trevor Philips. Nihilistic, violent anarchy given human form. Playing as him or next to him in GTA I didn't know whether to laugh or cry. All I knew was it was going to be a fun ride.

Max from Sam & Max. Utterly insane, violent and oddly well-articulated. What's not to love?

Torque, from the Suffering. Can relate at points. That and i like blondes (Jordan, evil ending).

I like the Civilization II advisors, especially Elvis! They add some great comedy to the game.

https://www.youtube.com/watch?v=FlTIk80uBPg