There is no way I could pick one.
10) Dual headlight mod - no more, "You got a headlight out" comments....bonus free mod!
9) Ceramic headers - no more bluing, less heat off the pipe, no more "You burned your pipe!" comments
8) Breather Re-route - drain the guck every 100 miles or so
7) LSL Foot pegs - better foot control feel
6) Open air box with K&N - bike began breathing freely...bonus people look inside and say "Cooool!" but "Where is the gas!?" To which I reply, "Magic."
5) RSS - cooled everything down
4) Adjusted the suspension settings - instant sharper handling... bonus free mod!
3) Amsoil - Gave the bike a completely new character.
2) Jardine CF exhaust - Felt like I unchained the bottom of the bike from an anchor, bike became so flickable + nice sound
1) EBR ECM - turned bike into freight train, tamed the cooling fan..... no more, "What's that noise?! What's wrong with your bike?!" comments.