Here is a list of the available weapon skins I found on gamebattles.
Gold
Chrome
Flame
Onyx
Arctic Camo
Garish
Crimson Omen
Team Insignia
Gold Omen
Blood
Child's Play
Deadly Cute
Desert Camo
Desert Digital
Jungle Digital
Imulsion
Haze
Flower
Electric
Thunderstorm
Ocean
Oil Slick
Team Pulse
Rainbow
Ubran Digital
Tribal
Tiger Stripe
Team Metal
Team Distress