Nexus 7 3g is probably the best choice I suppose. Pure android version without being modified, pretty fast, and fully function.
However it's not the representative of the whole android community since there are a way lot more devices which are weaker and running lower android version.
If you want your game to be pretty light weight and runnable on most devices, I suppose you choose a device with 1GHz chip, RAM 512, Adreno200, running either android 4.x or 2.3. Samsung P1000, Archos G8 are probably the good ones.
I believe pretty soon, android 4.0 and devices with dual core chipset like 1GHz x 2, RAM 1G will be the new trend, so you can try these too. Kindle Fire 1, Archos G9, G10, or Nook Tablet are some examples.