I work in Unity for my personal projects. As most of the world knows, it's a pretty lovely engine and quite an excellent working environment for me to stretch my legs in. I've dabbled in UDK a little bit, but Unity essentially is my home.
I enjoy making games with simple mechanics & polishing them up to be enjoyable. I prefer working on Multiplayer games, as they generally don't require the same time investment to play & enjoy, unlike Single Player titles. Nerf Everything is a pretty good example of my tastes.