This is actually a very tough question for me to answer. Out of my collection I would say my burmese python is my all time favorite because she's so gentle and beautiful... everyone loves her. I even let my little 7 year old cousin hold her, but with assistance of course.
If I could have any reptile in the world it would most likely be something like a dwarf crocodile, feas viper, or some kind of really extremely expensive snake like an albino retic *drools* or something super-duper rare. I also really like gaboon vipers and a lot of venomous and fat-bodied snakes. But honestly, I can't choose just one... I like them all