Sion and Nasus. Although these aren't often built as straight tanks, Nasus has Siphoning Strike which gives a huge one-off boost to his autoattack, plus having a slow, natural lifesteal and an AoE spell. For his part, Sion has Enrage, which not only gives an insane damage boost (+65 damage at lvl 5), if you get a last hit, it permanently increases your base health. You've also got a shield that can double up as a damage tool, a stun, and a lifesteal-based ult.
In a slightly different fashion, there's Cho'gath. His autoattacks, are a lot nastier than they seem thanks to Vorpal Spikes, he has a (rather hit and miss) AoE slow/damage, a silence, and a pretty nasty nuke. Plus there's the whole growing thing. It's entirely possible to hit 3k health by level 11 with him. However, he's a bit rubbish against towers, and Rupture is, as said, a rather uncertain tool.