"Waiting for Big Mo" is easily the most boring. That, or "The Gang Does a Clip Show", for obvious reasons.
EDIT: I just can't get over someone thinking "Whacked" was boring. Just off the top of my head, that involved:
- fixing the circuit breaker and discussing how to insulate oneself from electric shock
- discussion about society's unsolvable drug problem
- Bingo the shady people smuggler
- Nose clams and green people from history times
- the mobsters
- Peter Nincompoop and Buster the lawn jockey
- Dennis becoming a prostitute
- Dennis getting slapped
- Charlie and Dee on cocaine
- Cricket really starting to descend by getting addicted to drugs
- Cricket's sweet kettle drums
- hips and nips