Two choices. Both in the UK by a paintballer for paintballers
http://www.contourscotland.com/
You can also get a discount code if you like my teams Facebook (task force delta)
Why a contour?
They are cylindrical making the front view just the size of the lens,
they are tough and survive paintball impact (in my experience). We have had the case of the rear switch on the back cover dropping in from a direct hit from behind - sent to Matt of contour Scotland and dealt with on contour support
Waterproof cases are available, not essential as the camera is waterproof to a degree (not enough for diving) but also handy if you're worried about it being shot
It has the standard camera mount on the bottom and its own rail mount on each side
The lens rotates so you can mount anyway up
Many mounts are available, some come with the camera, I recommend the mask set as well for load more mounts
The contour plus 2 is top of the range and has many nice extra features
The contour roam 2 is about half the price but most specifications - the essentials such as pixels, frame rate match the +2
Plasma cam:
http://www.freewebstore.org/Plasmalightscouk/CAMERA_KITS/cat457033_809104.aspx
Also a cylinder
Mounted like a sight (anything that goes around the camera and can mount where you want), plenty of mounts around
Again they are tough and have been selected for paintball
The third choice is go pro (or a very similar aee action camera)
They are more bulky, but are the camera of choice in industry when a cameraman doesn't fit
The AEE action camera is a available from maplins, has the same chipset as the go pro, costs less and comes with all the mounts, waterproof case, a clip on LCD screen and a remote control
Go pro style needs the waterproof case for paintball to protect it - this will affect sound