Well ,i play Cho'Gath like Nunu
i am making Tank build in start,and last 2 items are AP ones
so,i make Mercury threads
Frozen Heart(armor and cd reduction)
Warmog's Armor
Zhonya's Hourglass(AP and Armor) or Abyssal Scepter(regarding enemies)
Then, i make Rabadon's Deathcap
No game lasted more ;D
Cho'Gath must be tank in start,mostly as supporter.And become kind of DD in end