I'd have to say the Ju290, the Pe-2, and A26 (depending on if you call it a bomber).
You don't see many calls for the Ju290. There have been a lot of calls for the He177A-5 over the years and quite a few uneducated calls for the Fw200 by people who think four engines magically make it a heavy bomber.
I'd say the most common requests for bombers now are the He111, B-29, A-26, Do217 and Tu-2.