SPAS-12 (Bell Shotgun)
Best shotgun in the game, granted there's only two types of shotgun. 8 shots of high power that should 1 hit KO Tribe A's. One thing about the game is I don't think they had time to model buckshot, so shotguns fire slugs instead, making aiming them a bit harder than expected. At least this one has nice sights to line up. Somehow makes a 'pump action noise' with each shot despite Anne having one functioning arm.
Benelli Shotgun
With less damage, only 7 rounds and no sights to line up, this is a piece of shit. Weirdly enough they spawn most of these at the ass-end of the game which means you have to use this thing against Tribe C's!
Anne holds it weird too, she 'hipfires' the gun, which is all but impossible to aim unless you've used it heaps before. I'd rather a Redhawk than this crap.
Browning Hunting Rifle
Good gun, only ten shots (more than any shotgun) but it hits like a truck. Pretty easy to aim too, but very low rate of fire. Get caught up close with this thing and you're screwed. You can get a lot worse than this weapon, but there's also a lot of weapons better than this one. Grab it if you can.
M-14 Rifle
A vietnam-war classic, this baby holds 20 rounds that almost does as much damage as the Hunting Rifle. Faster fire rate and good sights ultimately makes for a great gun. No automatic-mode but you won't need it anyways. Always grab this if you can find it! More common than the HK91 rifle as well.
HK91
Yeah so like an idiot I kept calling this thing the "G3", it's actually a HK91. Oops. It's basically just a reskin of the M14, holding 20 rounds, doing awesome damage and having different but also very useful sights. A bit more rare but always nab this one if you can too! I think it's based off of the nasty hunter dude's gun (the guy who is eaten by the compies) in The Lost World.
Norinco Type 56 (drum or stick mag)
Probably the best gun in the game in either form, does good damage, has a 40 (stick) or 100 (drum) round magazine and can be 'tap fired' very accurately. A single drum-mag Norinco can clear most of a map of raptors, it's just THAT good. Because I always wanted to save it 'just in case', I ended up not using most of them in the AAR, which bothered me quite a lot. X_X
Lindstradt tranq rifle
Same issue as the handgun version, why use this thing when I could just use a gun? I love how it's the same gun as from the movie, but it's just not practical. I wish the developers made these things more useful.
Lindstradt "Toxic" Rifle
There was supposed to be more than one of these in vanilla Trespasser, specifically two in the Ingen town, one in The Lab and the final one in Ascent Part 1. In the end all we can use is the Ascent one. And well...Why NOT use it? It's a one hit kill on anything aside from rexes! And it lets us bag the biggest predator on the island, the Alpha Rex. Thumbs up on this one.
.50 M82
Never used this in the AAR and it's purely static-mounted. Basically unusable because of how derpy the arm system is. In theory it 1 hit KO's raptors but good luck. There's also only like...Two in the whole game?...Again that damned two number! Bleh, don't use this thing.
.30 Browning machinegun
A weird mishmash of M2 .50cal and the M1919 .30cal, its a lot more useful than the barret sniper rifle is.
You still can't carry it around, so that limits it's potential, but in the AAR I made use of it to kill an albertosaurus and some raptors. Use it if you can, otherwise avoid.
And that crudely sums up all the weapons and how I feel about them!