I would prefer to see the other paintball player uncropped, as well as the guy in the foreground's feet. Also you see to have a tilt problem a bit to the right.
Nicely composed with the player's head on a third. An action shot might have been more interesting than crouching in cover. Mid afternoon makes for kind of craptacular lighting outdoors, but I guess that's when they play. Needs some CCW rotation.
OK, one of the kind of comments I hate: I wish that person in the background were on the other team and sneaking up on this one. :-) While it is a cooly shaped piece of whatever, I'm not sure why you chose to give over about a third of your image to the canister being hidden behind. It also looks like the image might be slightly rotated clockwise. I'd either go for a more extreme angle, or level it out.
I never played paintball, kinda looks like a BMX racer turned sniper. Lighting, focus, and dept of field are good. The subject dosen't really do much for me though.
Tell me that doesnt look like fun. Good color, fun game. I think getting slightly behind the shooter would make a better angle on the shot but would also add another target to the game :D.
You definately got the challenge part.......I think if you had zoomed out a bit, gotten rid of the big round thing on the left (most of it) and included the person in the upper right this might have been a winner in this competition.