16 lb Brunswick Command Zone. There are other balls (older and not as old) that I am still using effectively, but their roles have changed (aggressive balls when new now used when something with less traction is better suited to the lane conditions).
First saw it sometime around 1999-2000, and it looked to be in terrible shape ----and it was purple!. When the owner of the pro-shop showed it to me, I wasn't that keen on it, but ended up buying it, and it has been and still is my "slump-breaker" ball. Definitely a skid/flip type ball, though it's "flip" may only be a couple of boards, it is dependable.
What sets it apart from my other equipment is that it is still used in the same role (for heavy to medium-heavy oil). Still hits as good as the big boys as it's reaction has never changed, despite at least 3 drilling changes made over the years.