Undersized defensive linemen, to cause confusion, combat QB runs, and opening lanes for blitzers are some of the reasons to use defensive line stunts.
Antone' Sewell, Morgan State, Defensive Coordinator, walks us through five of his stunts that involve multiple defensive linemen. Coach Sewell was the DC at Bowie State when he filmed his course: The Darkside 4-2-5 Defensive System. The course has 22 lessons and is available on Glazier Drive.
The video below was taken from his lesson on D-Line Stunts.
Coach Sewell uses one-man stunts as well. You can see examples in the full D-Line Stunts video.
The names and responsibilities for his one-man stunts are:
(All of these means the player is going 1 gap inside with the exception of "nail." The nose crosses the center's face.
1) Punch - strong side end
2) Pinch - weak side end
3) Nail - nose
4) Spike - 3 technique