My all time favorite is Blood Waters of Dr. Z. It is unhinged from beginning to end in the best kind of way. The story is bonkers, the special effects and makeup are awful and the acting is worse but it’s all so good.
And to all the people new to MST3K you get the obligatory Pod People recommendation.
Space Mutiny is my favorite, but since OP already claimed it (now who will bring toys to the children!?) I’ll go with my close second, Overdrawn at the Memory Bank. It’s such trash and Raul Julia tears up every blessed scene he’s in. He only dabbles in dopples but his love for the cinemas is easy to reciprocate.
I’m very fond of Jack Frost. It’s as corny and delightfully bizare as one could want from a Russian mythology movie made in 1965 USSR, and the riffs are obviously great.
Tough question, because there are some great ones.
A recent favorite from the Netflix era has been “Cry Wilderness”. The movie was laughably bad in the first place, but that just made it great for the MST3k treatment.
So many great lines in there. Like the old man talking about how all the animals and nature are his family and friends and they voice the bird responding with “He’s not my friend. I’m not indigenous to this area. Please call the police.” That cracked me up so bad the first time I didn’t hear anything else for at least the next few minutes.
And also the running gag around terribly unsafe firearm handling: “BANG!”
That now goes through my head whenever a show just waves a gun around like an obvious prop instead of at least pretending it could be dangerous.