Erik the Slayer. For the most part he stays out of the way and his comment's aren't as annoying as some. I like seeing which weapons and armor he chooses out of the ones that my battlemage gives him. His choice of a Storm Atronach scroll in one battle totally suprised me.

You let him have a scroll? You're a more trusting soul than I am. I let him have a lightning staff once...he zapped me three times with it, and that was the end of magic item usage for him.

(Well, outside of his enchanted weapons anyway.)
Erik's my favorite follower so far as well. Non-annoying comments, very useful tank, somehow manages to avoid most of the dungeon traps, and he has an adorable tendency to stick his foot in it and amuse me besides. (Still my favorite example: "Caves sounded more exciting in the bards' songs." -- said while totally ignoring the werewolf directly behind him.

)
I just went through my first Dwemer ruin with him the other night...I love how he turned into something of a nerd, speculating over the Dwemer's disappearance and going on about how marvelous all the still-working machinery was. He also stays out of my mage's way and is actually decently stealthy for a tank. Definitely a keeper.

Although I do like Erandur, too. Nothing like two mages killing everything with fire and lightning to clear out a dungeon.