Tennant is my favorite, but I've gotten into the older stuff, as well. I really like the 7th and the 4th doctors. My kids will watch anything with Dr. Who, all the way back to the first doctor. My daughter went as a dalek for Halloween last year, and she's got a picture of the seventh on the wall in her room. It's a strange companion to her My Little Pony posters and Disney Princess decorations.
I wrote a short crossover last year,
Not a Day at the Beach .