I'm usually not interested in cult openings (e.g. the Blackmar-Diemer pawn loss) and go out of my way to discourage people from using them, but I have a soft spot in my heart for the Traxler/Wilkes-Barre variation of the Two Knights:
1.e4 e5 2.Nf3 Nc6 3.Bc4 Nf6 4.Ng5 Bc5!? (Threat? What threat?). I don't know if it's sound - it might be - but it's a lot of fun, and it seems a most fitting reply to the duffer's move.
At any rate, those who are interested in this crazy line should bookmark and utilize John L. Jerz's very useful
page on this variation, as well as Stefan Bücker's July 2007 Chess Cafe
column.
HT (of sorts): This month's Bücker's
column.
There are - some trivial, some not. I'll avoid specifying, though, as I don't want to give my future opponents any extra help!