I have a few favorites, although they're all out of the filk community. My favorite is "TALKIN' BUILDING Q BLUES" by Indianapolis filker (and degreed ethnomusicologist...) Barry Childs-Helton which is a send-up of the US-government-is-hiding-a-UFO idea. There's also Frank Hayes' "LIKE A LAMB TO THE SLAUGHTER" which is a shortening (hmm...perhaps a poor choice of words there...) of "Matty Groves". Actually, I sang the latter at an Open Sing once; the theme was "Long and Short".

-- Gary