Even though they're technically mortal enemies, you'd think they were best friends with all the time they spend near each other. The sniper fears the spy like no other, but the spy only wants to love and be loved. He's a romantic of sorts. The way he expresses his affection is rather unique, however, as it happens to involve a knife in the back. Hey, that's kinda like some friends in real life. Nice.
(These characters are from a game called Team Fortress 2, in case you aren't hip enough to know, which would be unfortunate.)