Favorite: The Big Store
Least favorite: A Day At The Races

Since the Marx Brothers were in a handfull of films...I will rank them from best to worst...

1-Duck Soup
2-A Night at the Opera
3-A Day at the Races
4-Monkey Business
5-Horse Feathers
6-The Big Store
7-Animal Crackers
8-Coconuts
9-A Night in Casablanca
10-At the Circus
11-Go West
12-Room Service
13-Love Happy

PS-I once played A Night at the Opera and A Day at the Races with Queen's A Night at the Opera and A Day at the Races, respectfully...and it practically works...just make sure you play "Bohemian Rhapsody" at the end of the opera part in A Night at the Opera!