My personal favorite is the Marushin P99 NBB.
I run duster in it, and with the suppressor mounted, it sounds like a mouse farting. lol
It came with a tactical light too, and makes for an excellent CQB Quiet Killer.
We have a field I play on that is fairly small, so we run pistols only matches every once in a while. About 70% of the time, my victim never sees or hears where the shot comes from. They just feel and hear the hit.
I also like the TM MK23 NBB, but it's a bit too large for me as a sidearm.
It's more of an offense pistol.