stick your bed in the garden and sleep outside...the advantages are twofold:
1- the rain will wake you up in time for paintball
2- the effect of the rain waking you up, will mean you will not go back to sleep when you get indoors, after leaping out of bed to get indoors.
Of course...sods law, suggests that in the event that you do that, it will not rain...you will not wake up, you will ,miss paintball.
Or, i will rain all night and you will get no sleep and be very pissed off...or it wont rain till 7am, but you will have left your keyes indoors next to all your stuff "so you dont forget them" and your mrs locked the door when she went to bed, and because she had the best sex of her life the night before, while you were in the garden, she is sound asleep and wont hear your screaming for her to open the door....
Get an alarm clock