http://www.nfl.com/rulebook/penaltysummariesSummary of Penalties
15 Yards
A tackler using his helmet to butt, spear, or ram an opponent. [gone]
Any player who uses the top of his helmet unnecessarily. [gone]
15 Yards (and disqualification if flagrant)
Striking opponent on head or neck with forearm, elbow, or hands whether or not the initial contact is made below the neck area.
Malicious unnecessary roughness.
http://www.nfl.com/rulebookThe new rules still show this:
Loss of 15 yards
Flagrant striking, kicking, or kneeing an opponent or striking him
on head or neck with heel, back or side of hand wrist, elbow, or
forearm………..………….....................................................12-2-11
And this vague note (same section):
Player using a helmet as a weapon……………..................12-2-15