The mini-crossbow can fire three types of darts:
- Tranquilizer Darts – Tranquilizer darts inflict non-lethal poison damage and are capable of rendering targets unconscious without killing them. Tranquilizer darts inflict 5 base damage on hit. Then, the target suffers 5 base damage every 2 seconds for 16 seconds (for a total of 8 ticks after the initial hit).
- (Normal) Darts – Normal darts inflict lethal damage on impact and have no special effects. With a base damage of 15, normal darts inflict more damage per hit than any other pistol skill weapon, and will take down any common trooper in a headshot at any skill level.
- Flare Darts – Flare darts serve as substitutes for standalone flares and will light up a nearby area when they strike the environment. Flare darts have half the light radius of normal flares. Flare darts can also be used to inflict lethal damage in the manner of normal darts, but only at 5 base damage.
With the ability to fire both lethal normal darts and non-lethal tranquilizer darts, the mini-crossbow can be used as either a lethal or non-lethal ranged weapon. Furthermore, the mini-crossbow is silent, making it suitable for stealth playstyles.
Leveling up the pistol skill increases the damage of all three types of darts. For tranquilizer darts, the pistol skill increases the damage per tick, in addition to the damage of the initial hit. At the master skill level, tranquilizer dart headshots take down common troopers at the first tick after the initial hit.
Darts have a straight trajectory up to the accurate range of 50 feet. After traveling 50 feet, the dart will begin its downward descent due to gravity. Therefore, against targets beyond the accurate range, it may be necessary to aim above the target to account for the downward trajectory. Although the mini-crossbow can accept the range modification, the range modification has no actual effect on the range of the mini-crossbow.
- The mini-crossbow is the only ranged weapon that can be used underwater. Majestic 12 scuba divers, the only human enemies encountered underwater, are armed with mini-crossbows.
- Enemies affected by the gas grenade or pepper gun will take four times the amount of damage that they would otherwise take normally. Thus, a single headshot is enough to knock them out at any skill level.
- If a dart hits a wall or a floor, it can be picked up again.
- The mini-crossbow is effective as a long-ranged sniping weapon when combined with the scope modification. For non-lethal playstyles, tranquilizer darts are the only ammunition that can knock out enemies at long range.
- Although the mini-crossbow is a silent weapon, a victim's death scream will alert nearby enemies.
- Enemies hit but not instantly incapacitated by tranquilizer darts can still move around and perform actions (such as activating alarms) while taking poison damage. If an enemy is near an alarm panel, it might be better to use another weapon.
- Using reload mods on the mini-crossbow reduces its long reload time in between successive shots.
- The crossbow can also be used for exploiting AI behaviors.
- Hiding and shooting enemies from a distance will provoke them into attacking, while friendly AI characters will not attack if they did not see the player firing the crossbow. As a result, the enemy may run into group of friendly AI that will fire upon the enemy.
- Shooting an enemy in the arm will usually do enough damage to the limb to make the enemy drop their weapon.
- Shooting a dart at a wall will make a sound, which will cause all AI to investigate it, letting the player slip by them unnoticed or take them out. The dart can be retrieved later.
- The crossbow is one of the weapons that Paul offers to the player at the start of the game. If it is not received from Paul, a mini-crossbow can also be found on an NSF trooper outside the Statue of Liberty.
- The mini-crossbow has its own attack sound defined, but it is never used because of a quirk in how silenced weapons are handled. The stealth pistol's firing sound will always take priority over any other firing sounds if the weapon is silenced, no matter if it is silenced naturally (like the mini-crossbow) or through the silencer modification.