Clawhammer banjo is a style of playing the 5-string banjo originating in the Appalachian mountains, and predating the more common bluegrass styles (known as Scruggs style, finger-style and also related to melodic 5-string banjo). It involves only the back of one fingernail and the thumb, and it looks more less like you're punching the head of the banjo. it's most common in old-time music accompnaying a fiddler. See Mark Schatz, Bob Carlin or Stephen Wade for excellent picking.

Clawhammer is/was the codename for the first 64-bit AMD processor. Clawhammer will (was to be?) be aimed at the desktop and low-end server market, while the more powerful sledgehammer will target the high-end SMP server market. The first clawhammers were expected to hit the market in the first quarter of 2002, however, nothing resembling clawhammer has shipped yet (as of March, 2003). As far as I can tell, the "clawhammer" and "sledgehammer" codenames have been dropped by AMD, as no articles published since early 2002 mention them.
See also: Sledgehammer, IA-64, Itanium

Clawhammer is related to/confused with frailing. In fact, most banjo historians define the term clawhammer as frailing *plus* the use of the thumb on the upper 4 strings (not limited to the 5th string as the strict definition of frailing goes), performing the 'drop-thumb' technique. See frailing.