While reading a random discussion on the English Chess Forum, I stumbled across a suggested line against the Evans Gambit. At first it looked so unbelievable, that I began to think it just might work. After 5.c3 Black just leaves the bishop hanging on b4, and hits back in the centre with f5! Although it was played over 100 years ago, credit for its rediscovery goes to the Geoff Chandler and Paul Cooksey on the RedHotPawn website. The only game in Megabase that I could find was a win by Blackburne against NN in a simul, put there are a couple of more games, and a discussion of its history here.
However, rather than pass off untested goods to the readers of this blog, I did feed the position into one of my engines. While ancient wisdom had that taking the bishop was risky, the materialistic computer thinks that this is the best. After 1.e4 e5 2.Nf3 Nc6 3.Bc4 Bc5 4.b4 Bxb4 5.c3 f5 6.cxb4 fxe4, 7.b5! is the right continuation, as 7. ... exf3 8.Qxf3 keeps White ahead on the material ledger.
Based on that I am loathe to recommend it for anything other than blitz or rapidplay, and obviously only as a surprise-surprise weapon. Why the double surprise? Simply because the Evans Gambit is once again rarely seen in the wild, even at the usual hack-happy club level. So it may be a while before you get a chance to play it.