I had a couple of recent serious games when, true to form, I played gambit lines, but it was the first time I had used them in serious games, and I haven't covered either of them at my website. The games contain a fair number of mistakes, but they were 25 minute rapid games.
Game/Gambit #1 - The Geller Gambit
The more successful experiment was in the Geller Gambit (yes, I've also re-added 1.d4, 2.c4 lines to my repertoire, having been attracted to some of them back in my childhood). 1.d4 d5 2.c4 c6 3.Nc3 Nf6 4.Nf3 dxc4 5.e4 b5 is the normal move-order, but I stumbled into it via 1.d4 d5 2.c4 c6 3.Nc3 dxc4 4.e4 b5 5.Nf3!? (5.a4 is the normal move, according to the Chesslive.de database, where White generally regains the pawn) 5...Nf6.
I had a close look at this line with someone from my local chess club back in 2014, but have to admit that I don't recall much of the theory. My 6.e5 Nd5 7.Ne4?! was clearly inferior to 7.a4 and 7.Ng5, but was not punished. Also, I could have got a strong attack with 13.f5 or 14.Nxe6 (both of which I actually looked at during the game, but didn't see far enough ahead). The experiment paid off in the end though, and I have every intention of continuing to try out these Queen's Gambit lines.
My impression is that the Geller Gambit has been held suspect for many years, but that "the Ginger GM" Simon Williams has advocated it in some recent videos of his. I associate Simon Williams particularly with the Dutch Defence (1.d4 f5) and some crazy queen sacrifices, notably this one. He also tried the interesting deviation 1.d4 d5 2.c4 c6 3.Nc3 Nf6 4.Nf3 dxc4 5.e4 b5 6.Qc2 against Andrey Sumets at Hastings 2013, but lost.
Game/Gambit #2 - Rubinstein Four Knights
The line goes 1.e4 e5 2.Nf3 Nc6 3.Nc3 Nf6 4.Bb5 Nd4, from Black's point of view. It's well-known to be a sound line for Black, where White often ducks out of the complications with 5.Nxd4 or 5.0-0. I had recently taken this up in my online games, and sacrificed the pawn on e5 in several of them with good results. However, I hadn't learnt many of the ideas behind the sacrifice of the pawn on e5, and so in this serious game played too "automatically" in the opening and didn't get enough compensation. Indeed, if I had found 10...Bg4! I would probably have gone on to win.
The games are available here: http://www.viewchess.com/cbreader/2017/3/1/Game190376437.html