Surprisingly enough, you won't be using the AT-14 Pistol all that much in F.E.A.R. While it's a decent enough weapon, and is a bit more precise than many of the weapons in the game, it still lacks much stopping power, and forces you to click your fire button each time you want to fire a round, leading to a bit of trigger fatigue if you rely on it overmuch. It can, however, be dual-wielded, which can be a cheap but useful tactic in multiplayer, especially if you can land headshots with decent frequency.
Although the RPL Sub-Machinegun is wildly inaccurate at medium ranges, or while you're moving, it does have the benefit of having plentiful amounts of ammo available for it, especially early in the game. Almost all of the Replica forces you're going to come across in the first half-dozen levels or so will pack an RPL, allowing you to amass huge amounts of ammo. Its large, 50-round magazine and quick reload time also make it a handy weapon when you're just trying to put a few dozen bullets in the air and hope that one or two actually hit your foe.
At close range, the RPL can actually get most of the grunt-level enemies into a kind of crude stunlock, where they'll take so much damage so rapidly that they can't manage to fire back at you before they're dead. Just watch out for the reflex shots when they're going down.
VK-12 Combat Shotgun
Now we're talking. Every FPS game has to have a shotgun - it's a federal regulation - and we're happy to tell you that the VK-12 is a perfectly kickass example of a boomgun.
You know the drill by now: it's a shotgun. It's one of the most powerful weapons you're going to find at close range (a good shot can actually explode an enemy from the inside out), but is going to be almost completely useless at mid to long-range. That said, you're going to be getting up close and personal often enough to justify carrying the shotgun around almost all the time, especially since a single round to the chest is almost always going to be enough to take down a Replica soldier.
One of our favorite things to do with the shotgun is to turn a corner, fire at whomever we see, then retreat a bit and wait for them to come to us. When they round the corner, just blast them in the face; a good shot will actually shear their heads from their bodies quicker than you can say "Jack Thompson." And you just can't underappreciate that kind of comedy.
G2A2 Assault Rifle
The G2A2 is essentially a more powerful and more precise version of the RPL, albeit one that's also slower to fire and has a smaller magazine size. It's still a worthy upgrade to the RPL, though, especially when most of the enemies you encounter start dropping it instead of the RPL. Although it's not flashy, there's going to be enough ammo for the G2A2 to make it worthy of lugging around for most of the game.
The ASP Rifle is about as close as you'll come to a sniper rifle in F.E.A.R., at least until you come across a Type-7. In actuality it's more akin to a scoped MP-5 that's locked into burst fire mode; although it does have a scope, and can zoom in, there's just something that's kind of annoying about only being able to fire off three rounds at a time. The good news, however, is that those three rounds are going to punch a hole through almost anyone that they hit, even if you go for body shots. On a per-bullet basis, the ASP Rifle is one of the more powerful guns in the game, but ammo is quite limited for it, so use it while you can.
10mm HV Penetrator
The 10mm HV Penetrator is F.E.A.R.'s version of the trusty old nailgun. Shooting out polycarbon bolts at a frighteningly quick pace, and with excellent accuracy, the Penetrator will likely be the sharpshooter's weapon of choice for much of the game. Although it's a fairly weak weapon, it's almost 100% accurate when zoomed, so even though it doesn't have a scope, players who are good shots should be able to get headshots with relative ease. Failing an instant kill, the Penetrator is still decent at taking people down with rapid-fire shots, which leads to amusing deaths on the part of your foes, not least because of the way they'll often get pinned into nearby surfaces when they finally die.
Note that, despite the fact that this weapon is called the Penetrator, it really doesn't seem to be all that effective against armored opponents. It works best against the fleshier of the Replicas.