rock stars do it all the time
I suggest wearing a very light amount. Too much eyeliner can look bad on ANY gender.
As for style, eyeliner looks good with anything except for preppy or jock type clothing. Scene, punk, emo, goth or any style that's out of the box looks good. Just don't do too much too fast or else you'll be labeled as a poser.
Hope that helps.
Yes. Depends on which style of clothing he wants to go with. I personally like punk clothing with eyeliner on my men (with Sid Vicious hair, yesplz). There's also goth wear, 80s pop wear, designer, etc. Eyeliner goes with almost everything, I think it's most important to get the hairstyle right though. Certain hairstyles make eyeliner look emo, others make it look sexy.