If I could only have one, it would be a Specialized Epic FSR with a Brain shock on the rear and lockable front fork. It would allow me to have a very functional mountain bike for mountain bike riding and a serviceable rigid road bike. It doesn’t have much capability for carrying things and it is slow on the road but it does allow for both kinds of riding. In fact, I have one (of 2) at my daughter’s house for exactly that reason. It works on-road and it’s an excellent off-road bike.