wide out corner back or if you can hit hard safety
anything but defensive linemen
Waterboy.
Benchwarmer.
If you are now 17-21, then Defensive Back, you should be able to run at least a 4.42 40. However, you need to build some muscle, there aren't many players in the league under 190lbs.
The safest position to play in football, with the least amount of injuries, is either the punter or the kicker.
Cheerleader.
running back
Either lineman or fullback
Q.B, running back, Wide Reciver
Defensive tackle
RunningBack