I don't usually play 3's, but when I do it's off-tank Volibear. And it is good.

volibear, darius and probably mundo

these 3 have tanky stats and can build pure defense tank items but still dish out the pain

for ap singed

Teemo.

Volibear, by far.

boots 1 -> Warmogs -> Anything with health/armour/MR -> Attack speed item (Ionic spark is good)

GG

I think that amumu is a really good tanker, plus he can use sunfire cape and despair to brinng out amazing farming abilities. He also does 2 stun moves.

NAUTILUS. He has not one, not two, not three, but FOUR forms of crowd control.
1. Root on his passive
2. Pull on Dredge Line
3. Slow from Riptide
4. Knock up/stun from Depth Charge
AND a hefty shield that can deal tons of damage. If Naut isnt focused down, his shield-buffed auto attacks will shred an entire team with few or no damage items.
You absolutely cannot get any better than that for a solid tank on TT.

Personally, I believe Amumu is by far the best tank. Build him semi-tanky but still having a lot of health and ap he can dominate a fight. Especially building him with Rylais, giving him health and a slow that can be used with his w giving major CC to your team. Also, those stuns are great too.

Voli? (I don't think so)
Cho is ok...
I LUV AMUMU.
Singed is pretty beast. I love him.
Rammus is just... an amazing AD counter.
Blitz is pretty good...
A lot of the Bruisers or Tanky DPS are quite good... like Riven, Darius (gotta love him?)
Mundo is decent when built correctly, but he's not really a tank.
There are quite a few more that can fit the role of a tank or a kind of tank.