Do note, that these are subjective to me, so there will be some servers that don't fit the vanilla TF2 feeling very well, those will be put into the "honorable mentions" section, I'm only including them 'cause they really are cool servers! so do check em out! :D
castaway - runs weapon reverts and cool custom maps that fit the art style
the furry pound - furry group #1
tiny kittys girl pound - furry group #2
loser puppy fag pound - furry group #3
zesty jesus - servers ran by e-celeb tf2uber zesty jesus
twerkborea - a wretched hive of scum and villainy (jk its a good time)
pbphoenix |IP: 45.79.222.172:27015 - runs super cool custom 2fort maps
shounic trenches |IP: 45.62.160.71:27015 - runs 100 player tf2 with maps designed for it
balloon race 24/7 |IP: 74.91.113.210:27015 - runs balloon race, a fun and creative custom tf2 gamemode
alpaca pizza party |IP: 104.153.104.12:27015 - runs a most interesting custom shopping center themed map