Since we hear so often about gun nuts, and a few members claim the title themselves, here are pics, courtesy of Brownells. Feel free to choose your own for your avatar.
AR-15-CASTLE-NUT
Benelli-FRONT-SIGHT-RETAINING-NUT
Mossber-ACTION-SLIDE-TUBE-NUT
R-308-BARREL-NUT
Springifled-M14-CASTLE-NUT
SW-MAGAZINE-CATCH-NUT
AR-15-CASTLE-NUT
Benelli-FRONT-SIGHT-RETAINING-NUT
Mossber-ACTION-SLIDE-TUBE-NUT
R-308-BARREL-NUT
Springifled-M14-CASTLE-NUT
SW-MAGAZINE-CATCH-NUT