Go to Tusk Act parts for more information.
Tusk is the stand of the Corpse Parts, wielded by Johnny Joestar, which allows him to fire his nails. (You can't fire nail bullets/shots in the game excepting when using Tusk Act 4, its final act.)
E - Tusk will punch using its tiny arm, dealing no damage.
Tusk act 1 looks like a pink neotenous alien creature which features yellow stars on its body.
Hand corpse + Standless = Tusk
This stand has no working offensive moves, using E will bug your player, making you unable to jump, roll, and unsummon tusk. This can be fixed by dying or resetting.