Mordin Solus' old student in Mass Effect 2, I can't remember if Shepard, or Mordin shoot him - But it's damn depressing, their race seems so fragile, and Mordin really gives them all character, and then bam we kill one (given you choose the bold Renegade move), and the poor guy just drops.
There are also the little monkey type critters that are on some planets, they seem quite rare for the most part... But you can't help yourself when you see one, they must die. So you shoot them, and then you look at it and see a dead little monkey thing... And you have to kill them on the Krogan planet too!
:(