I've used:
Marcurio
Jenassa
Annekke
Derkeethus
Stenvar
Erik
Roggi
Faendal
Uthgerd
some Stray Dogs
(I've also suffered once through the companions' questline and their idea of "followers"...

)
Jenassa clearly was the best for my purposes indeed. But I have killed her a couple of times because she was strafing around like an idiot between the target and me. She also got me killed a couple of times by strafing around like an idiot between some archer and me (I play rather fragile characters who die from a single arrow, even if that arrow was aimed at the idiot follower while I hadn't been spotted yet). And she has died in a Falmer encounter once or twice.
I liked the Stray Dog very much, even though I don't particularly like dogs normally. Both times, he randomly disappeared after a while though.
Erik is very adorable, and I'd rate him 2nd best after Jenassa.
Stenvar I also liked quite a lot. He was the very first follower I tried (after I had been traumatized by forced followers as in the Companions' questline, I played for a long time without any followers, because I thought that they would be just as bad as Farkass and the other imbecile dogs). Stenvar I recruited because I simple couldn't find a way to Winterhold that wasn't guarded by a deadly snow sabrecat or murderous snow bear or pack of fierce ice wolves, and I really wanted to travel to towns on foot before using the carriages. I thought that a follower might be capable of cleaning the path for me, and so he did. I've been using followers ever since.
Faendal looks creepy, Derkeethus and Annekke didn't manage to show any kind of personality or adorability. Uthgerd alerted the whole population of dungeons as soon as we entered by the front gate, and then she died quickly.
Marcurio was annoying in many ways. He kept one-shotting stuff so that I didn't get any experience at all anymore. And his
"I am an apprentice wizard, not a packmule... ah well, but make it quick" line annoyed me really quickly really bad. I think I could cope much better with Lydia's
"I'm sworn to carry you burden" than that; but I've never really been tempted to ask a housecarl to travel with me. Their job is to be a guard of my premises and to keep burglars out.