Actually, the Inquisitor is the worst. It lacks the damage per bullet of the Emperor and sheer dakka of the Repeater, and its large magazine isn't really something you need on a secondary. That being said, I mostly use Repeater and Underboss, and Commissioner on my shotgun loadouts. Been toying around with the Crossbow too but it doesn't seem effective in my hands.
Dirty Harry for me 95% of the time, but that is because I am VS and I am not a fan of our pistols most of the time. I have success with the beamer but my hand suffers because of it (as does my accuracy). On my NC I almost always use the desperado and on TR its Emperor or Repeater with commish on certain loadouts/situations.
Beamer. Accept no substitutes. I have no issues hitting its max RoF and remaining accurate. Its got better hipfire than the commish/uBoss, way better sights then other pistols available to VS, and with it I always have a suppressed weapon w/ me. The Manticore is a close second, but it fires too slow for my liking for not that much more damage (actually less DPS past 20m).
I own the Underboss, but I've recently switched back to the Beamer. It's fast and accurate to a stupidly long range, reloads quick as hell, and as you noted has a suppressor. If you get used to just fanning LMB to dump half the mag into someone, it'll kill just as quickly as any other pistol in the game. It's not the one hit or two hit kill everyone loves so much. But it sure looks embarassing on someone's killboard when you take them down with one.
Cerberus ' cause I like the look of it... and I have got used to its short comings. Underboss on my alts.
In TR its inquisitor. NC its Rebel. VS its Manticore. On infil that i dont do much its usually crosbow or underboss.
TS2 Inquisitor all day, every day. That fast refire time allows me to shoot as fast as i can click, and i click very fast. I've been accused of having hacks or macros that make my side-arm seem like it's on rapid fire huehuehuehuehue
Rebel with flashlight every day, every loadout. Stupidly deadly gun - 250 damage is two headshots to kill or 4 body shots, and has almost twice the max damage range of other pistols, which is HUGE. I run out of ammo with my Reaper sometimes, and the swap to the Rebel is seamless. It's like a battle rifle sidearm.
As TR, either the pocket SMG (the starter pistol, the TX1 Repeater) if I am planning on being in more CQC environments, or the NS-44 Commissioner, as it is amazingly effective at range, and the OHK headshots versus infiltrators is wonderful.
