For the absolute most unique gun possible on the field...
Leave it stock.
Nobody ever does that.
It's hard to go wrong with Krylon camo paint (it's a matte paint). If you really want a good, durable finish, you'll need to clean the parts to be painted thoroughly. Apply a coat of primer. Allow it to dry properly. Apply your paints. Allow to dry properly. Finish with a clear coat. I don't know if clear coats are available in matte.
If it doesn't have to be a masterpiece, skip the primer. Personally I prefer a more natural battle-worn look, so camo coats are dusted on thinly, lightly and repeatedly. After a few games and a little rain, it blends and wears nicely.