The followers I've used most often are Cicero, Lydia, and Serana. I do use them as pack mules, but also usually give them the best armor that doesn't fit with my character. What I mean is that if I'm a lightly armored character (which is most of the time) and I find some good heavy armor, I give it to my follower. Whatever I won't use but is too good to give up, I give to my follower.
I don't often take followers, but when I do I often try to outfit them with better armor than I. I can't make a character without it being a blacksmith, so I always craft high protection, high damage, highly enchanted armor to my followers. I love 'em too much to outfit them with anything but the best.