Well, I am partial to Chihuahuas.. BUT they are so hard headed. they actually are easy to train, but they really only listen to one person and really only care what one person has to tell them.
I have a dachshund/chihuahua mix as well, and he is a good breed I think to get. plus, you can easily find one to rescue, even as a puppy. he listens VERY well. he loves to play and cuddle. he likes to run around and have fun, go for walks, but at the same time he doesnt go crazy if you dont do something one day and just sit at home. the only issue I have had with him is he needs his anal glands expressed a lot, but that's pretty common in a dachshund. I also have to be a little careful of his back, but since he is a split between the two, he doesnt have quite the issues a normal or mini dachshund will. he might have alittle min pin in him as well, but he is definetly mostly doxi/chi.
and I got him super abused, unsocialized at 11 months old.. and you would never know =]