Yes; they do exist; and it is a pleasure to work with them; and, I have/had the honour of working with a few. I was reminded of them when I read this post of ZapperZ about his own TA-ing experience and what it taught him:
After that semester, I TA’ed only for one more semester before I received a research assistantship and didn’t have to do any more teaching work. Still, I think I learned quite a bit in executing that responsibility. I certainly sharpened my skill as an instructor quite a bit, and learned what worked and what didn’t. But most importantly, I realized that students will try to get away with as much as they can if you let them.
Of course, needless to say, TAs who try to get away with as little as they can are also plenty!