Since I stared playing not so long ago and I am a "noob" at Pokemon Go this is what I believe to be my best Pokemon so far.
Tauros CP158 my HP is 3/37 because I used it in a recent fight which I got served.
My favorite for defending gyms. Insane HPs and it's not even maxed out yet. Real nasty too, because it's so low on CP that it's usually first in line against attackers so it really whittles down the opposition. Just gotta make sure not to place it until gym prestige is really high to accommodate more teammates. Otherwise your own team will be hard pressed to rank up the gym.
"Best", of course, is relative to your goals. My highest CP is a cp928 Pensir that I renamed "D.BruteSquad". My OG Squirtle (at cp13) is my original homeboy so that's gotta count for something, right?
I just started, so my Pokémon are still growing... But my best is a CP 101 Drowzee; which is highly ironic, because I was never a fan of him in my Game Boy/DS games.