Pawn on the rim : A Bobby Fischer recommendation
Fischer once recommended 2.h2h4 against Modern Defense, though he never seemed to have played it himself.
Several top GMs like to push their h or a pawn. And for lots of GMs pushing the pawns at the rim has almost gotten a routine to either win or draw.
See here the Jobava miracle from 2014, where the pushing of the a pawn helped to gain a crazy draw in a seemingly lost position :
And how about the famous h pawn in the famous miniature Larsen-Spassky ?
Let's look at some Modern Defense with a quick h2h4 now :
If you look at the games of GM Magnus Carlsen, you will see that he liked to push a and h pawns in his games. In some games I believe he even pushed both pawns very far ahead.
Also in the endgame a far advanced h or a pawn can be a big advantage. Of course, in the endgame, one must be careful not to lose that pawn, without compensation, when it gets weak in some cases.
Happy h pawn pushing !