I love 'em all too, but ten that "pop out" at me would be:
Bud Abbott Lou Costello Meet Frankenstein
Hit the Ice
Hold That Ghost
Abbott and Costello Go to Mars
Bud Abbott and Lou Costello in Hollywood (yeah, MGM)
Mexican Hayride
The Time of Their Lives
Abbott and Costello Meet the Invisible Man
The Wistful Widow of Wagon Gap
Pardon My Sarong