Badass guys?

[Nya-chan Production]

Any badass, but ordinary guys (no mechas and lots of shooting and slashing involved - focus on the guys themselves).

One example would be Ryuuji from ToraDora!, that's what I have in mind. More would be welcomed.

[Taite]

Not sure if my definition of badass-ordinary guy is the same as yours
When you say badass-ordinary guy, I think of humans who lead a normal-ish life, but still maintain their badassery.

Kyouya from Ouran (or any of the Host members, really.)
Morita from Honey and Clover.
Kenji from School Rumble.
Isaac from Baccano! (as well as many other characters)

[Dar]

Some of the guys from Gravitation perhaps?

[Kanti13]

Train from Black Cat
Akira (movie, anyone)
Maybe Vicious from Cowboy Bebop
Ciel from Kuroshitsuji. Even though he is young he's totally badass! One of my all time fav characters.

[CodeZTM]

Hatsaharu and Kyo from Fruits Basket fits the bill. Kind of..

[Nya-chan Production]

Some of these were fairly helpful - totally forgot Bebop crew and guys, f.e. ^^;

[Hagaren Viper]

Masaru/Marcus from Digimon Savers/Data Squad is a street fighter when he's not beating up Digimon.

[Kariudo]

Seiji Sawamura -Midori Days
Rock -Black Lagoon
Haseo .Hack//roots (and G.U., and Trilogy)

I CAN'T BELIEVE NOBODY HAS MENTIONED KAMINA FROM TTGL
there's enough of him not in a mech to make it worth mentioning

[Enigma]

Sephiroth - Final Fantasy 7/Advent Children
Mugen - Samurai Champloo
Spike - Bepop

Btw Kari, Fuck Kamina |':

[Kitsuner]

Akagi, perhaps?