I used to play the Grob (1. g4) often, when I was studying it, and was able to achieve many wins against higher-rated players with it, but I perceive that the opening has been over-analyzed. Too often do players have a ready response against it, and that I think makes a difficult opening nigh impossible.
I actually have achieved better results with the obscure and universally scorned Barne's Defense (1. f3) than with the Grob. A number of players waste time during the game pondering a sortie with their Queen against my kingside or actually performing it with dismal results.
While I appreciate that the Grob is difficult to play, it receives what seems to me fanatical and unreasoning hatred from some quarters. I have read "refutations" of the Grob many times that failed to persuade me. I maintain the opening is sound and cannot be refuted. As with other unpopular openings, a draw can be achieved if both players play precise moves. I have seen 1. g4 d5 2. h3 e5 3. Bg2 Nc6 set forth as being better for Black. I would counter with 4. c4 Be6 5. cxd5 Bxd5 6. Bxd5 Qxd5 7. Nf3 and now the position seems to me by a slight degree to favor White, which stands to gain a tempo with Nc3, unless Black opts to trade a bishop for a knight (recapture with dxc3, and Black gains a tempo via O-O-O, but White's King has a good post at c2, and I like White's chances).