Well, I guess the largest is Watermelon, our L027a Royal Panaque Plec.
He's only around 7-8" now (a little over 1/3 possible full size).
Most of my fish have got plenty of growing left in em and are no match for CFC and Paul et al
And also the larger of the two BGKs in the tank, though this one is around an inch or so bigger now (probably getting past 8" now)