Cherry Dr. Pepper.
Love this stuff.
I also love grossing roommates out when we stop somewhere and get something from a soda fountain (like at McDonalds or Burger King or Jack'n'the Box.). I'll mix Coke (Cherry Coke if they have it) with Dr Pepper. Unless it's a Pepsi vendor, then I'll get orange or a clear soda (Pepsi tastes too sugary for me).