Cardio bro... I like to stay fairly balanced.. I want to be able to go out and run a 5K at a decent time on any given weekend...
I love mountain biking (10-15 miles at a time), hiking (5-10 miles a pop) and running (3-5 miles).
I've bulking up with no cardio before and I feel sluggish.. I like to be able to hit up the volleyball court on the beach during the summer... play softball weekly... play some basketball.. you know, live an active lifestyle.
I find that regular cardio keeps my heart, lungs, and legs in shape to do those types of things.