Of all time?
Luger
P38
BHP
Glock 17
Tie between B92 and SIG 226
Lots of good ones mentioned, but if you're talking about ones that actually see/saw service, I'll stick to my list.
Some other good ones include Walther P88, other Glock models (prob 19 being the most common these days), CZ, P7, P210, and potentially the new M&P (way too early to tell). But none of these have seen the service/duty that the originals have seen.
cc