Very hard to select just one!
But although it's a great one with many classic scenes, I always thought the end scene of "Three Little Beers" was a big let-down. Such a lame gag after such a great short.
"An Ache in Every Stake" - also lots of great classic scenes: the stairway, the bowling with the ice blocks, the kitchen scenes, especially Curly shaving the ice. But I had to go with:
"Hoi Polloi" -- The Winner! Again, lots of great stuff. Plus the bonus of a good incidental music score, and perhaps my favorite Stooges short of one of my favorite supporting players, Phyllis Crane.