Old "greco" was good at the latvian gambit (my favourite opening). Good luck in catching him though :D. Another gambit I thought of whilst reasing this was the elephant gambit: 1. e4 e5 2. Nf3 d5. But I must say, the latvian works very well in match play and otb.
Caltrop coefficient

I got bitten by a sort of Blackmar-Diemer the other day: 1.d4 Nf6 2.f3 d5 3.e4 de 4.Nc3. You have to watch these things.

In the article I linked to above, McGrew says that "caltrops are mid-sized pieces of metal shaped rather like giant jacks with sharpened points." Soldiers would sprinkle them on a river bed, so that when the horses stepped on them, the cavalry would go down. Sounds kind of cruel, but basically what he means is openings which may not be sound, but have conceiled traps.
In his Chess Cafe column Gambit Cartel, Tim McGrew introduces the concept of the Caltrop Coefficient, basically the number of well-conceiled traps that a naive opponent playing natural moves might fall into when facing a given opening. The openings he mentions are the Damiano Defence 1.e4 e5 2.Nf3 f6, the Latvian Gambit, the Budapest Gambit 1.d4 Nf6 2.c4 e5, the Blumenfeld Gambit 1.d4 Nf6 2.c4 e6 3.Nf3 c5 4.d5 b5, the Blackburne-Hartlaub Gambit 1.d4 e5 2.de d6, the Felbecker Gambit 1.d4 e5 2.de Nc6 3.Nf3 Bc5 and the Soller Gambit 1.d4 e5 2.de Nc6 3.Nf3 f6. In a later article, he looks at the Schilling-Kostic Gambit 1.e4 e5 2.Nf3 Nc6 3.Bc4 Nd4 hoping for 4.Nxe5?! Qg5.
Can anyone name some other trappy openings? Are there any trappy openings that might hold up at correspondence speeds? Are there any players you know of who specialize in trappy openings? McGrew mentions Lev Zilbermintz, and probably players like Claude Bloodgood or Clyde Nakamura would qualify as well.