Someone who says or does something that is so ridiculous that you literally have no way of expressing your feelings except shouting out a random phrase, thus "sweet face".
Guy 1: *says something really gay*
Guy 2: Ooo, yeaah, sweet face!
Guy 1: *Pops his collar*
Guy 2: You have a sweet face. Seriously.
When one guy sees another walking down the street w/ an ill concealed boner, the following ?????? steps occur:
1. Guy 1 sees the unfortunate boner
2. Guy 1 thinks about why Guy 2 might have this boner
3. Guy 1 thinks about the things that might make this happen to him, too
4. Guy 1 stubbles across an arousing memory or idea
5. Wham-o, sympathy boner.
Guy 2: *boner*
Guy 1: Aww that sucks *sympathy boner*