Warning: Missed opportunities! (Mate in X)

So I was playing this blitz game a couple of minutes ago and had a pretty good feeling after the game, it went pretty well and I was confident I hadn't made too many mistakes. Boy was I wrong! 

I fed the PGN to Deep Rybka when all all of a sudden, in the middle of the analysis and game, I saw a variation appear with an # at the end of it.. I was like "wtf.." So here you go, you try to find the move I missed! Happy puzzling!

White's last move was f4

ALTERNATIVELY for extra stylepoints!