Schweinehund
Member
Amumu
There are no tanks in Dota
puck is best tank.
Like who can take the most damage without any items?
Spectre or Syllabear is the tankiest (until Bristleback is put in).
Alchemist/Dragon Knight are runner up. Alchemist with his ult up is probably the tankiest, but its not always up.
The only hero that can really taunt is axe though.
Edit: If you mean who's the best initiator it's a bit of a toss up. I think earthshaker is the best, but it could easily be sk or tide or enigma as well. BM/Puck are not as good but still very good to have. Clockwerk/Axe are behind the other ones I listed, imo.