Gaff, an undergarment used to conceal or hide male genitalia, used primarily by cross-dressers and transsexuals

Gaffe means an error

Generalized AMBER Force Field, part of the AMBER molecular bond simulation software.

Gaff rig, a spar used in certain sailboat rigs

Playing cards with special marks or adjustments that are used to achieve effects in card magic.

Gaff Tape, or Gaffer tape, is a type of cloth-backed adhesive tape used frequently in the film, television, and theatre industry.

Gaff, is an artificially created fantastical creature (the name comes the fishing term, as they were used at sideshows to "hook" people in), examples include the Fiji mermaid

Hakapik (or gaff), a club for killing seal cubs.

Gaff (fishing), a pole with a hook used to land fish

Gaffs, the metal spikes worn on the inside of the feet by lineman & tree climbers, to assist with climbing.