The Viper is a semi-automatic, rapid-fire sniper rifle manufactured by Rosenkov Materials. Rosenkov developed a patented automated-release system that assists with thermal-clip ejection, shortening the Viper's reload time. This rifle is popular with military snipers, who appreciate a long-range gun that can snap off multiple shots in the blink of an eye.
On harder multiplayer difficulties, enemies' increased health makes this weapon markedly less effective, with lightly protected enemies often requiring 2 hits to the head to bring down. Still, when used properly, it can take down light enemies more efficiently than the single-shot Mantis.
The Viper's main weakness is its poor performance against heavily protected enemies. It's mediocre against armor and well-shielded enemies, and, in order to be effective against heavy enemies many shots must be fired, causing a user to expose themselves for longer durations than they would with other sniper rifles.
Probably the most efficient method of using the Viper is with a Salarian Infiltrator. With the character's passive class power maximized for weapon and headshot damage, and the Extended Barrel mod attached, a consistent and accurate player can pop heads off basic trooper enemies very quickly even on Silver difficulty. They can also easily dispatch shielded troops such as Marauders and Centurions by removing their shields with a maximum-damage Energy Drain followed by a timely Viper headshot.
An update on June 21 has drastically increased the performance of the Viper with better damage and lowered weight. At level X it now deals the same damage per round as the N7 Valiant I as well as having the same weight as Indra X, making it the lightest sniper rifle in the game after being fully upgraded. Since it is of uncommon rarity, this is very easy to achieve.
The weight improvement makes the Viper an excellent choice for power-reliant classes like Engineers or Adepts who still want to be able to use a sniper rifle. A Viper X can be used as a substitute for a scoped Carnifex, with a 10x zoom instead of 2x, making powers more effective over a long range. The Viper's status as an uncommon as opposed to a rare makes it much easier to level than the Carnifex, as well.
Even on harder difficulties, any character which utilizes Overload can make great use of this rifle, or any sniper rifle in particular. Once shields are gone, a Viper X can easily kill many of the infantry class enemies, such as: Assault Troopers, Centurions, Geth Troopers, Geth Rocket Troopers, Cannibals and Husks with one well placed shot to the head. Even if it doesn't kill the target instantly, the next will. Armor-piercing rounds or mods increases the effectiveness against armored targets drastically, putting it on par against organic targets.
In particular, Asari Adepts do very well when using the Viper as their sole weapon. With Stasis, you can consistently perform headshots on multiple weak targets and still have Biotic Explosions to fall back on for heavy units. Cryo rounds can be used to further halt a target's advance once Stasis wears off.
The Viper's semi-automatic fire makes it a good no-scope weapon. It can be a good complement to melee-based classes like the Talon Engineer, who, fully upgraded, can usually take out or severely wound enemies at close range with the Omni-Bow. Used in this manner, the Viper can easily mop up stronger enemies, while giving the player the option to hit more distant targets after clearing out the immediate area.