There are many good gambits, from tactical ones such as the Fried Liver Attack, the Evans Gambit, or the King's Gambit, to positional ones such as the Volga Gambit. But there are many bad gambits, such as The Omega Gambit(1.d4 Nf6 2.e4?) or gambits with one trap in mind, and nothing else (Blackburne-Shilling Gambit). Are there more of such gambits?
lativian, halloween, wing, englund, elephant, freds, colorado, danish gambit, tennison, and budapest gambit of the top of my head. These gambits are unsound and a proper response will have the gambiter in a worse position.
Some gambits I do like are kings gambit, smith morra, evans, queens, scotch, benko, lisitsin, staunton, fried liver(Na5), froms.