I always liked Mojo Nixon's cover of the old David Peel song "I Like Marijuana."
Peel's "The Pope Smokes Dope" is funny as Hell ,too.
Cheech and Chong's "Up in Smoke" is a classic.
If you want to go back to the late 1920's Cab Calloway's "Reefer Man" is a great one too.
He performed in an old W.C. Fields movie in the early 30's with his Orchestra,so there should be video of it out there somewhere?
Calloway was a wild man on stage.