I am showing my age ;) but I still use Chessbase 8 for my chess database. One of my favourite features is the Dossier where it shows your repertoire and what the percentages are and what your performance rating is. Last year for instance it showed that I scored 18% with 1.Nf3 d5 2.g3 (rated purely on games from 2001). i had played 1.g3 the odd time so I decided that if, over the year i got either 1.g3 d5 or 1.Nf3 d5 i would go for the King's Indian Attack just to raise my score. And I did :) So in the interest of scientific research I decided to do the same thing...this is from my personal database of over 11000 correspondence, OTB, and blitz games.
My lowest two as white are two of my most hated lines as White :
1.e4 e5 2.f4 d5 3.exd5 e4 and 1.e4 e6 2.d4 d5 3.Nc3 Bb4 4.e5 c5 5.a3 Bxc3 6.bxc3 Ne7 7.Qg4
(in the interest of putting some positivity my best numbers are against 1.e4 e5 2.d4 d6 3.d4 exd4 4.Nxd4 Nf6)
As Black my best is surprisingly the Queen's Indian 1.d4 Nf6 2.c4 e6 3.Nf3 b6 and my worst is the Colle 1.d4 d5 2.Nf3 Nf6 3.e3
maybe for 2010 I'll go back to playing 1.d4 d5...i enjoy the Queen's Gambit Accepted, the Tarrasch and the Semi-Slav. And if I happen to beat some Colle's too...so be it :)