Ratslayer has a very high critical multiplier of x5, making it the gun with the 3rd highest multiplier (after alien blaster and Euclid's C-Finder). This fact alone makes the Ratslayer a very powerful gun; a player with a critical chance of 20 (or higher) would score a critical strike on every successful hit.
Ratslayer also has the smallest spread of any 5.56mm chambered weapon, making it a valuable choice for sniping targets at great distance.
Ratslayer ammunition and repair parts (varmint rifle) are easily found early on, though retrieving the weapon can be a hassle with the Wild Wasteland perk, as the rodent of unusual size is a formidable enemy, especially for low level players
Pairing Ratslayer with the 5.56mm Match ammunition type (which has a spread multiplier of 0.65) makes it one of the most accurate guns in the game, allowing you to take full advantage of its higher magnification to pull off incredibly long range shots. Doing so while crouched allows even players with very low sneak skill to pull off shots from stealth, which in turn greatly increases the odds of scoring a critical hit. All of these factors together make Ratslayer a truly devastating weapon, provided the correct situation arises.
ps3 When looking through the scope, the screen might appear green and pink, making it impossible to use the scope. This may happen on any scoped weapon (including binoculars). To fix this, just save the game, shut down your PS3, then restart the game and the problem should be fixed. [verified]
pcxbox360 It appears that the night vision scopes for varmint rifles work off of the in-game clock, activating at 6:00pm while the sun doesn't go down until around 7:00pm. [verified]
xbox360 When using the "player sight" final/first kill cam, the scope will momentarily turn clear, no matter what time of day it is. [verified]
pc The onHit effect for this weapon is defined as "Dismember only" (the weapon will only calculate the chance to sever limbs), as opposed to the varmint rifle, which uses "No Dismember/Explode" onHit effect (all limbs hit by the weapon will remain intact). There is a bug associated with the "dismember only" effect, which will immediately alarm all enemies in the vicinity of the killed enemy. This is not triggered by the sound level of Ratslayer, which is the same as the standard varmint rifle's sound level, but by the onHit effect itself. Because of this bug, this weapon is mostly useless for sneak attacks, as only one sneak attack is possible before enemies become alarmed. (A mod that fixes this is available at http://newvegas.nexusmods.com/downloads/file.php?id=41827). [verified]
xbox360 This is a bug that only happens while being in third-person, in motion, wearing the NCR Ranger patrol armor, and holstering Ratslayer: the weapon clips inside your body and only shows the barrel of the gun protruding through your left shoulder. This can be fixed by drawing the weapon, stopping motion, and holstering it again. [verified]