White to move,

PawnG2-G4 checkmate.

Next person can post a scenario.

After g4 black takes hxg3 e.p.

Weird one, because white is just up a lot of material and there are no stalemate tricks for black yet, so almost any move wins.
I'm thinking about the mating net here, 1. Bg7 (threatening Rh6#) g4 2. f4 gxh3 3. gxh3 Rxc5+ but now I realised I actually gave black a chance to draw, because the rook will be untouchable since black king is in a stalemate if I take it! The position will still be winning for white, because I can go with king to d5 and block the rook check with my bishop, but that looks kinda unnecessary. In a blitz game I'd just play Bd6 so that I don't accidentally stalemate my opponent and proceed to promote a-pawn.

Oh, wait, I thought the red arrow indicated black's last move, i.e. it took the bishop. But I guess it just means it's attacking the bishop?

Sze, bg7 g4 xg4 kg5 bh6 is mate.

So bg7 is easy win

Edited 12/7/2015 10:40:53

You're right Koala! I did not see that pattern, nice one. Missing Bh6 i thought I needed to cover g5 somehow to create a mating net.

Yup, it is indeed a forced mate in 5 here :)
Game Link here: http://www.chess.com/echess/game?id=119065276

@WCT, sorry about the arrow, I analyzed the game an the engine added a "random" arrow. Did not mean to have it in the screenshot.