Taken from NFL.com
15 Yard Penalties
1. Chop block.
2. Clipping below the waist.
3. Fair catch interference.
4. Illegal crackback block by offense.
5. Piling on.
6. Roughing the kicker.
7. Roughing the passer.
8. Twisting, turning, or pulling an opponent by the facemask.
9. Unnecessary roughness.
10. Unsportsmanlike conduct.
11. Delay of game at start of either half.
12. Illegal low block.
13. A tackler using his helmet to butt, spear, or ram an opponent.
14. Any player who uses the top of his helmet unnecessarily.
15. A punter, placekicker, or holder who simulates being roughed by a defensive player.
16. Leaping.
17. Leverage.
18. Any player who removes his helmet after a play while on the field.
19. Taunting.