I've been told I am the worst at telling jokes, probably because I don't really have a sense of humor which is almost certainly necessary in order to execute jokes effectively.
Case in point...a conversation I had today went on like this.
My friend: I hurt my pinky.
Me: (remembering that yesterday was a holiday and also trying to be funny I asked) How, BBQing?
My friend: No, mountain biking.
Doh - not funny! I am such a dork. This, I know.