CMC, ARGold, or Geissele if you want to get an aftermarket trigger. Which type depends on what you're using the gun for.
IMHO, those are the only three I'd spend my money on. If I didn't want to buy one of those three, I'd be running a standard mil-spec or a modified mil-spec (polish, springs, and creep reduction set screw).
I like the top of the line adjustable Geisele enough to have purchased two of them to replace both of my two stage Jewell match triggers. The Jewel's were top shelf 10 years ago, and still feel excellent, but the Giesele triggers have a noticably faster lock time. That is not big deal shooting off a rest or bipod, but when shooting offhand at 100 or 200 yards, a precise trigger is mandatory. I have an SSA in a 15-22 that is really good too.
I know that there are probably some other pretty good triggers, but since I am not interested in single stage systems, I automatically disqualify them from my list.
Any Mil spec trigger will be fine. Giesele, timney and other triggers don't always strike hard enough to set off military primers. That's my personal preference, I'm not into all these fancy triggers.
I like the SSA-E trigger, but a lot can be accomplished with properly stoning a stock trigger. It all depends on use. I've got a single stage trigger in one AR lower that I generally use for longer ranges, an SSA-E for a 300AAC setup, and a stoned stock trigger for SHTF.
My home defense carbine has a mil spec trigger. My other ar's have timney competition 3lb trigger single stage. It's less expensive and probably the best for the money at $190. It's crisp, has ~0.2mm of overtravel, and ~0.3mm to reset, which is less overtravel and reset than any geissle offering
I have a CMT and 2x Colt Mil-Spec triggers that feel just as good as my 2xALG QMS triggers. I thought those were the bee's knees until I tried a LMT 2-stage trigger. That trigger is nice. I then purchased a Geissele SSA-E and that blows everything out of the water. I had a Timney single stage 4lb. trigger and that left a lot to be desired.
The Geissele is definitely better than a regular old USGI, but like it was mentioned before what are your intentions with the rifle?
I have shot Geissele, CMC, POF, Rock River, and a handful of mil-spec triggers. I still own the following...
Geissele:
G2S (x2), SSA, SD-C, SSA-E (x2)
a POF single stage 4.5 lb and a PSA mil-spec. I've put thousands of rounds on the Geissele triggers and never had issues with harder primers like some may claim.
I just put a SSA-E trigger in a new build. I've been very happy with it thus far. Geissele makes a great trigger and they have outstanding customer support.
Any Mil spec trigger will be fine. Giesele, timney and other triggers don't always strike hard enough to set off military primers. That's my personal preference, I'm not into all these fancy triggers.