For me, it would be TsunamICS 1.5.
Of all the ICS roms I've used, I found this to be Smooth and most features for daily driving are working, though I have not encountered any feature that hasn't worked. Gaming works great as well! OH and the Android OS and System Battery Usage only goes up as much as 29%, no more than that. And Screen Usage on "Auto-Brightness" never goes higher than 35%. ^_^
Battery Life is astounding! From morning on minimal use from 100%, I went down to 89% the next morning. On medium to heavy use (ex. games, youtube, web-browsing, etc..), I would go down to 35% by the end of the day, just enough to cover the night.
Rom: TsunamICS 1.5 (AOKP_Milestone_4 based..)
Kernel: Semaphore ICS 0.9.1
Its just wierd though, the development thread for TsunamICS 1.5 suddenly disappeared. ~_~