HTF
HTF can be used if referring to:

1.) How the fuck

2.) Happy Tree Friends

3.) Hard to find (Ebay users)

Or the not commonly used:

4.) Hand to forehead
---------------------------
---------------------------
1 HTF did that happen?!

2 Lmao HTF is really funny but gory.

3 Wow that item is so HTF!

4 Oh my god, why did you even do that...HTF