Standoff is my current favorite. I also like playing CTF on Slums. Cargo is a great map for Domination and Search.
I primarily play objective base modes, and I've found that some maps work great with some modes, and not with others. So, its hard to have an overall favorite due to that variety. Standoff is still my favorite though, as I love Search, CTF, and Domination on it.
"We do not stop playing because we get old, we get old because we stop playing." -- George Bernard Shaw