i enjoy the tranq rifle because it is closest to the mini-crossbow from deus ex with poison darts you could shoot at dudes to knock them out.  it's most fun when you hit a dude with it but he keeps on patrolling until he eventually just passes out.  i also appreciate seeing the dart sticking out of them so you can tell where you hit.  against augs it's a little weird though because you can shoot them in the metal robot shoulder and somehow that works . . .  also the tranq to the head death with merciful soul xp seems accidental.

either the machine pistol or the p.e.p.s. is my least favorite.  the machine pistol because it's everywhere but i like to play non-lethal, and the p.e.p.s. because it sounds like a non-lethal crowd-control weapon but when i've tried it out it either just knocks everyone down after which they all get up and try to kill me, or it also throws a box at them that i didn't expect, and now some of them are dead.

Never used the PEPS. Now the Revolver with explosive rounds on the other hand was fucking brilliant.

10mm Pistol and Revolver. I wouldn't even carry anything else on my second playthrough. They leave more inventory space and if you stick with two weapons it's easy to stock up on more ammo than you'll ever need.
 
The revolver is better than the shotgun once upgraded, and with area damage too. 
 
The pistol has the hole one shot head shot thing going on. 
 
The only reason to use the combat rifle is if you want to play the game as a straight shooter, in which case the homing bullets come in handy.

I dig the Stungun, has been vital in my first playthrough. Next favourite is the Combat Rifle fully upgraded, although the 9mm fully upgraded with armour piercing upgrade is pretty sick.

Least favourite is definitely the Machine Pistol, especially with the Rifle, it doesn't really need to be in my inventory.

I have been rolling with the Sniper Rifle for much of the game, and I haven't even used it once, so am now thinking is it really needed at all? Might sell it and buy the Rocket Launcher instead, OR if I can find the Silenced Sniper I will use that instead. Anyway, where can I find the Silenced Sniper Rifle? I believe you can't use a silencer on a normal Sniper?

Assault rifle/crossbow(never used it). I did make good use of the tranq rifle and the PEPS(great nonlethal weapon) But the 10mm I fell in luv with, in that with a few upgrades it was my fallback lethal, and it did it's job.

The pistol + every upgrade you come across = BEAST.

@Kandycane2029 said:

I've yet to use anything other than the tranq rifle.

i love the tranq

I really hated the heavy MG. Sure it spits out burning fury like nobody's business, but it takes so long to wind up, you're usually dead or severely injured before you get to waste anybody.

On the other side, we have the stun gun. 1-hit KOs, messes up the bosses, perfect for stealth. My weapon of choice.

@TheHT said:

Most favourite is the pistol, silenced with laser, etc. Really satisfying to just pop out of cover and land a stealthy headshot. Though there's something really satisfying about using a fully upgraded combat rifle to just start dumping into dudes.

Least favourite's the revolver. Never picked one up, not even to see what it was like. Well, ok, except for the revolver that was infront of Isias, but that was only because I was worried if I left it...

SPOILER WARNING: Click here to reveal hidden content.

he'd shoot himself.

Haha, I did the exact same thing. I had never touched the revolver until that point. I picked it up (for the same reason) and carried it out of the room and then immediately dropped it.

Tranquilizer Rifle and 10mm Pistol are my favorites!

Crossbow is the best.

Favorite: Lethal Takedowns.

Least favorite: I didn't spec my character toward combat efficiency at all, so I found myself really disliking the Heavy Rifle.

I like the Rocket Launcher in theory. In practice however it's ammo is way way too limited to make it of any use past the 1st boss.

Not a fan of the Heavy Rifle either, plus it's ammo if a bitch to lug around.

The silenced pistol and the combat rifle are my favorites. I think they handle really well.

I love the pistol once it's upgraded and silenced. There's ammo everywhere for it and it's nice and reliable.

I played stealth and non-lethal so my favorite was the gas grenade and least was PEPS.

Been happy with the pistol & tranq gun. Thought that the slienced sniper rifle was useful especially in act2's surprise attack. Think that the peps (stun shotgun thing) along with the normal shotguns are the least favorites.

@Jack268: The silenced pistol was my favorite. Pew pew! :D