The companion characters in Mass Effect are living, breathing, loving characters with unique personalities and motivations. They are also pretty boring. They could learn a lot from HK-47, the assassin droid from Star Wars: Knights of the Old Republic.
"Correction: Assassination is my primary function. I also possess excellent hearing and can bend spoons."
The Star Wars saga proper isn't exactly known for its wit and humour, at least it wasn't until 2003, when BioWare introduced Darth Revan's droid Friday to players of Knights of the Old Republic. Against a backdrop of cookie-cutter Star Wars archetypes, HK's dark humour and general disdain for all living things brightened the day of many a gamer, even if he persisted in calling them meatbags.
"Observation: I am a droid, master, with programming. Even if I did not enjoy killing, I would have no choice. Thankfully, I enjoy it very much."
This murderous machine, voiced expertly by Kristoffer Tabori, became an overnight sensation amongst Star Wars fans, which lead to roles in Star Wars: The Old Republic II: The Sith Lords, Sony Online Entertainment's massively multiplayer Star Wars Galaxies, and most recently BioWare's own Star Wars: The Old Republic. He's even got his own action figure.
"Clarification: When I said 'death' before 'dishonor', I meant alphabetically."
I'd go as far as saying that HK-47 is one of the most important video game characters of all time, a completely original creation that managed to transcend the source material, changing the way fans perceived the Star Wars franchise.
"Observation: I am awesome."