This just popped into my head. I'm sure we're all familiar with the heist film and all the tropes that go along with it, along with a few variations. Some good examples of heist films include:
- Gone in 60 Seconds
 
- Heat
 
- The Italian Job
 
- The Ocean's films, and
 
- The Usual Suspects
 
There are many others, of course.
My point here, however, is that there is a subgenre of heist film that has strong comedic elements that come to the fore. Not to be confused with heist films that have comedic relief, 
caper films are primarily comedies.
One strong example is 
Dirty, Rotten Scoundrels with Steve Martin and Michael Caine, a 1988 remake of the 1964 
Bedtime Story, which starred Marlon Brando and David Niven.  
I absolutely love this film, and will see it again soon after a long time, and maybe I'll even check out the original. In thinking about this, I cannot for the life of me think of any films that would also fit in this category, beyond, maybe, the 
Pink Panther films (of which I'm unfamiliar with, btw). 
Help me discover more capers. List your favourite capers here, and what you like most about them.
Edit: Oh, and enlighten me, because I haven't seen many heist films either, so I'm not sure which would be more comedic vs. more serious.