Pyjak

Mass Effect 

 
They are first encountered when admiral Hackett wants Shepard to find a surveillance drone that was watching over the Geth. It found the Geth were invading, when the surveillance drone tried to escape it was shot down and crash-landed on a planet that had several 'monkey' (Pyjak) colonies. 
Shepard is tasked with finding the hard drive of the surveillance drone after finding out a Pyjak had taken it. Shepard can either search each Pyjak (Paragon) or gun them down (Renegade). 
The search will lead to a mine, in which the Pyjak carrying the hard drive is found in the very end of the mine cavern. Once found Shepard has to fight his way through a large group of Geth. 
 

Mass Effect 2

 
The Pyjaks appear on Tuchunka (Krogan DMZ), apparently they are a pest. They steal anything they can get their 'talons' on, this may be a shiny, beeping data pad or food. Ratch, the Krogan merchant, tells you that they are a pestilence and if Shepard wants a discount at his store he can take part in a mini-game. This mini-game has Shepard using a rocket defence system to kill Pyjaks that want to get to the food stores. There are three waves of Pyjaks. Once completed Shepard can buy some Pyjak meat to give to Urz (a former varren pit-fighting champion). 
There is a Pyjak that can be found in the 'infirmary' area of Tuchunka, this Pyjak will sit on a crate and Shepard will have the choice to punch it.