Mini-crossbow

The Mini-crossbow was specifically developed for espionage work and accepts a range of dart types (normal, tranquiliser or flare) that can be changed depending upon the mission requirements.

The Crossbow is one of the weapons Paul offers to you at the start of the game. If you don't pick it up there, a NSF troop outside the Statue of Liberty has it. If you don't get it there, NSF troops will have it. If you don't get one there, you'll find it on the ground in later areas.

Tactics
The Crossbow is extremely useful in pacifist runs. It's the only ranged weapon that can knock out enemies, so you'll be relying on it a lot. Try and put a scope on it ASAP, since you'll need all the range you can get. Accuracy mods will also help, even if you do upgrade your Pistol skills. Range mods will help get over it's low accuracy range, so use them on the Crossbow as soon as you get them. Clip mods do not work with it, so get used to having to reload after four rounds.

In a non-pacifist run, the Crossbow is almost useless, even when it's upgraded. It's darts do little damage, Tranq Darts take a while to kick in, and Flare Darts fun to use, but are rare.