Fawkes from Fallout 3 was my favorite companion. Also GLaDOS and Handsome Jack are two of the best villains in recent gaming history.

The entire NPC cast in Silent Hill 3 and 2

Groose, GlaDOS, the narrator from Stanley Parable (Does it even count? lol).

And of course, Mr. Saturn.

"DO YOU WANT SLUMBER? KAY-O!"

"BOING!"

The Merchant from Resident Evil 4. Loved his quotes! "Got some rare things on sale stranger!", "Aaaah I'll buy it at a high price!"

Maybe Bob from Animal Crossing. He's the best.

Navi.

Difficult to say..

Maybe someone from Rune Factory :p

The frogs that save your game in Mother 3. The message the last one gives you only adds to the tension of the end.

I think she May be the one...

Jokes aside I dunno, probably Impa (?)