Birdy

Cowboy Bebop

Dragonball

Flame of Recca

Gundam Wing

Hunter x Hunter

Inuyasha

Mononoke Hime

Oddments

Outlaw Star

Ranma 1/2

Rurouni Kenshin

Trigun

Yuu Yuu Hakusho

Reptile
The story never really gives a reason why, but Koganei's eyes are usually drawn with strange slitted pupils, which you can see quite well here. They're not exactly cat-like, more reptilian, I'd say...
 
Added: 12/9/07
 
Reptile