Body: Sgt. Stalker from the Ultimate Battle Pack
Head: Airborne
Mask: Temple Guardian Snake Eyes
Webgear: Red Fang Ninja

This was one of my earlier customs, made back in 2009. He's had some tweaks done since I first did him, mostly accessories.

He now sports a Temple Guardian SE mask and Red Fang ninja webgear. The whole body is a Stalker figure.
This wasn't a custom that I was clamoring to do, it was one that I had seen done, it was easy, and took little time.
The benefit of customs like that is doing something with all the extra weapons and gear you accumulate, as well as doing something useful with all your duplicates.