metro is quite taxing, but only if you turn the dx11 settings on (at least from my experience)
other than that, i would have to say Supreme Commander (1) with some of the mods that reduce construction times, but that is a processor intensive game
though, i also realized that stalker: Call of Pripyat really ate resources, when i was running it (with the complete mod) i noticed at 3 seperate times, it maxed out my processor, hard drive, and used 1.3GB of video memory (from what i remember, metro only used 800-1000MB when i was playing it)
now if that isnt enough you could use actually benchmarking software (like unigine heaven benchmark is what i use)