It really depends on which character I'm playing as. Erik the Slayer's the perfect travel companion for my Nord, what with his eagerness to please and cheery disposition. He always sounds delighted to have his inventory accessed: "No problem! How can I help?" As for my Imperial, she looks for someone who's easy on the eyes and tough on the field. Aela fits that bill. It's not all business, though - Aela's both her battle buddy and her wife.

My Dunmer, well, she's got no stomach for sentimentality. Marcurio's her man when she's delving into crypts and Dwemer ruins, as he seems to have a familiarity with them, while Jenassa's her go-to girl for anything above ground. Earthen passages 'don't agree' with her, after all.
Nice post.
I always think it's my characters, and not me, that like and choose their followers. If I'm roleplaying a character that is going to use followers, I go thru a few at the start to see who has the right chemistry. When the right follower has been found, they'll be there till the end of the playthru. So I can't say I have a favourite, but each character does.
My first character (seems so long ago now) was a Nord Warrior. He settled on Marcurio, which worked well because Marc would make wisecracks at the expense of the more serious Nord, "Oh, I suppose you're going to look in every chest now." The combat worked well too - I gave Marc all the staves which were greatly boosted by his magic skills
pic
http://www.flickr.com/photos/joseph__x/6452737749/in/photostream/lightbox/
Vid taken on my mobile
http://www.youtube.com/watch?v=WbN3cSBBmP0&context=C4904701ADvjVQa1PpcFMD4H0DLcechQrVk2N7JTSUF18jE_a1c_M=
I thought the mage-warrior combo worked wll in battle, so my next character (a pure mage) was going to use warriors. Being a High Elf, Ursana didn't get on to well with Vorstag, who was a bit po-faced tbh. She wasn't all that unhappy when he came to one of the most gruesome ends possible: http://www.flickr.com/photos/joseph__x/6509912027/in/photostream/lightbox/
She eventually settled on Cosnach, who she found adorable, even though he did drink all her invisibility potions that she gave him to carry: http://www.flickr.com/photos/joseph__x/6544555937/in/photostream/lightbox/ Despite his faults, he was the perfect bodyguard. http://www.flickr.com/photos/joseph__x/6573908279/in/photostream/lightbox/.
http://www.flickr.com/photos/joseph__x/6615750849/in/photostream/lightbox/
Aranea was just perfect for my Dunmer daedra worshipping badass. Together they solved a lot of problems for Skyrim's Dark Elf population.
http://www.flickr.com/photos/joseph__x/6732900355/in/photostream/lightbox/
http://www.flickr.com/photos/joseph__x/6760487683/in/photostream/lightbox/
Finding a companion for a 62yo Imperial wasn't easy http://www.flickr.com/photos/joseph__x/6906975975/in/photostream/lightbox/ Ahtar the Jailor died at the hands of Forsworn Briarhearts and Hagravens, and her husband Belrand used to get on her nerves when she took him out. http://www.flickr.com/photos/joseph__x/6940401119/in/photostream/lightbox/. Her favourite was her lady in waiting - Jordis the Swordmaiden
pic http://www.flickr.com/photos/joseph__x/6806032982/in/photostream/lightbox/
Vid (AverMedia game capture): http://www.youtube.com/watch?v=Q-nZ9A3JSDM&context=C4c47a2bADvjVQa1PpcFMD4H0DLcechcQpfjbTm3WJgBJVPuNl6w4=