I recently beat a higher rated player as White in an unusual line of the Morra Gambit Declined.
4...g6 looks like a slightly inferior way of declining the gambit, allowing White a classic two-pawn centre. After 5.cxd4 the Chesslive.de database gives 569 games with 5...Bg7 (probably best) when White is scoring 59.6%.
Over the board I spent a while deliberating over 5...d5 6.exd5 or 6.e5, and correctly selected exd5. I was playing by analogy with some Göring Gambit Declined lines that I'd looked at before, where Black has to beware of the d4-d5 pawn push if White can get a knight out to c3 without it being hit by the pinning ...Bf8-b4. I gave 6.exd5 Qxd5 7.Nc3 Qa5 in the notes, but most often played has been the retreat 7...Qd8, albeit with White still scoring a hefty 71.2%.
I got very tempted by the possibility of trapping the black queen. Fritz says that Black can survive, but admittedly has to walk a proverbial tightrope. Overall I thought it was a pretty well-played game, though as usual at club level there were some mutual inaccuracies.
Meanwhile over at my gambits site I'm working on updating the Urusov Gambit coverage, as that is rather out of date at the moment.