So, greek gift is very useful way of breaking your opponents king position, and theres been a loads of examples how effective this gift can be, even GM level! I recently had a game where I had a chance to play this nice sac, which after I simply raiped my opponent until he resigned. I remember how after his resignation lots of people came to look my game and started analyzing it. It was vey flattering.. My opponent was too suprisingly good natured, and thanked me for a good game. Though, when analyzing the game, he sweared pretty much..
So here is the game: