Since there is no topic yet about MST3k.. I just had to create one!
I am a big time MiSTie and love the Rifftrax shorts and certain full movies they have done. Cinematic Titanic is also great but I haven't yet seen any of the movies, aside from the samples.
My favorite episodes off the top of my head (in no particular order) are:
The Dead Talk Back
Cave Dwellers
Gamera vs Guiron
Hercules Unchained
Moon Zero Two