This isn't a real glitch, but its very effective, so I call it a glitch. I found it a couple months back, but I haven't used it in a while, but now I'm putting it back into my scheme.
HOW TO DO:
#1. 1st off, it has to be a pass play. USER control one of the players running a route, hike the ball, and run about 3 yards with him. If you did this right, he should stall for a second then begin to run again.
This allows one of your other players to occupy a zone, then the player you controlled runs into it unguarded for a big gain, or a short gain. Works very well, just watch out for the blitz.