In my opinion, this is simply the most fun ability to use in the game. When a squishy character gets too close and you crit your Parrrley for an insane amount of damage, it is such an amazing feeling. Gangplank can be a bit low tier, but nonetheless the ability is fun to use. A little extra gold doesn't hurt either.
My biggest crit damage was 1819.
(2 Infinity Edges, 1 Phanton Dancer, Trinity Force)