Any version of NBB MK23 I've used. They perform incredibly and have absolutely earned their reputation for that, but fuck me if they haven't all been the saddest thing the moment I pull that equally sad trigger.
I want a pistol that goes bang, not that sounds like a trapped fart popping out. Purely goes down as disappointing for me because I didn't think it'd bother me as much as it did, alas, disappointment is a very personal/subjective thing.