Someone who finds very little funny, but what they are amused at is generally the misfortunes or even the pain of others ?
This person won't laugh at a comedian for example but will roar uproariously at someone who lost their job, even if they are friends with him, and also I found them laughing their heads off at one of the nastier death scenes in a final destination movie 
Is it possible to "teach" someone to have a sense of humour that is, well, a bit more mainstream?