(From the ones I've owned/heard) Best bass in the department of
-Amount: Beyerdynamic DT 770 (way too much).
-Fun: Sennheiser HD 25-1 (punchy, warm, slight reverbations, little bit bloated in comparison to better headphones)
-Implementation: HD 650 (not the tightest, not the most uniform, not the most low-reaching bass, but it sounds very good)
-Definition: Stax SR-404 (uniform, tight, good bass detailing, reaches very low, too little slam)
-Realism: AKG K1000 (too bad that it rolls of below 50Hz)
-Honorary mention: PS-1 (I only listened to it briefly a few times but the bass was extremely good. I can't depict what exactly I liked but I liked it a lot.)
The Stax has an excellent bass, there's just not a lot of impact. Wish I could hear the Omega IIs someday.