You can take any single survivor. Who's it gonna be?
For me it's got to be Ned. His free search action usually gets me better weapons quicker than most and when used with the flashlight he can usually find what your looking for amongst the equipment deck.
Kim's Lucky skill is very useful, and Phil starting with a pistol is also useful. Hard to pick really but anything helping combat is a good start. Even gaming nights Thaigo with reaper has a serious advantage.