I've seen every single episode of South Park, and here is a list I've compiled of my top 10 favorite South Park episodes of all time!
I put a link to the episode where you can watch it, as well as a good clip from each episode! The clips may or may not be spoilers!
#10 - Free Hat - S06 E09
#9 - Imagination Land Trilogy - S11 E10-12
#7 - Make Love, Not Warcraft - S10 E8
#6 - Smug Alert - S10 E2
#5 - Mystery of the Urinal Deuce - S10 E9
#4 - Cripple Fight - S05 E3
#3 - ManBearPig - S10 E6
#2 - Ginger Kids - S09 E11
#1 - Scott Tenorman Must Die - S5 E4