it's not only one alone, depends on the purpose.
but 1st place holds my little HK:
1.
HK P7 M13 --> the first I purchased - my fastest - and veeeeerry cute
2.
my custom 686-6" (PPC-bull-barrel, PPC-grip, chrome-nit.-finish) --> top precision and very heavy -- best for PPC course
3.
686-2,5" --> small, but quite nasty up to 25 yds
to be continued ...