I main Mundo.
Very fast jungle clear, super beefy if built right, buffs to Spirit Visage make it actually viable against mostly magic compositions. Clears deal a lot of damage to the spider, and make it super easy to stick to people and close gaps, Ultimate sustain and speed buff in conjunction with speed shrine and cleavers make it very hard to escape from.
Singed for similar reasons, basically any "super tank" with hardcore pushing abilities, gap closers/slows. Cho'gath as well, mostly because in a 3v3 theres a lot less damage potential then a 5v5 and he can get really tanky and almost become unkillable.
Teemo. because LOL No wards.
I would however like to see Bulwark available on TT, I find currently theres no reason to build an Aegis, but a bulwark with the extra 200 health and Magic resist might be worthwhile.
I also think that you need to seperate Deathcap and Zhonyas again. Its super easy to go like Deathcap Cho or Teemo and wreck just because you get the huge AP and the Zhonyas active, as well as it making you pretty tanky. Playing Diana on TT with the old Blackfire Torch and Wooglets (That gave +movespeed) pre-nerfs was hilariously overpowered.