Its normally part of the patzer attack, where beginning players opt for a fast developing attack on black's f7 pawn by playing an e4-Bc4-Qh5 formation (If black played e5). Its probably the very first thing I learned to defend against when I first started playing online blitz chess. In the case of using it against the Sicilian, black has excellent results after 1. e4 c5 2. Qh5 e6 3. Nc3 Nf6 where white has to lose time repositioning the queen.

At Hikaru's level of chess, I imagine Qh5's surpise value is that it pretty much removes all of black's home preparation, assuming black doesn't know you like to play it ahead of time ;)