Pretty much anything Looney Tunes related was great, and yes, I too enjoyed the episodes with Wile E. Coyote & Road Runner.
I would say the funniest Looney Tunes episode ever was with the whole "Hassan-Chop" deal when Daffy and Bugs went to Arabia and found gold. Needless to say, Daffy is greedy as usual, but Bugs handles things great. Of course, that's until Daffy decided to make a genie angry because he thought the genie wanted the gold too.
The episode where Daffy is Robin Hood, well, that's the second funniest episode in the series I think.