In the increasingly popular fandom for BBC's Sherlock television series, Jimlock is the 'ship name' of the pairing of Sherlock Holmes and his nemesis James (Jim) Moriarty.
This pairing is particularly popular because of the rivalry between the two (in the fangirl mentality, apparently male rivalry=gay relationship), and because of the similar degrees of intelligence that the two men possess.
"Hey, you watch Sherlock? Epic! I totally ship Johnlock."
"No, that's old. Jimlock is where it's at, now."