Flash a smartphone with vanilla Android ROM
Well Google only develops "vanilla" Android (called AOSP for Android Open Source Project ) for some selected phones (the Nexus Series). 

Manufacturers use this as base for their phone's OS. So you probably won't get a "vanilla" Rom from your manufactures, but there are probably a few AOSP-based Ports for your phone. (CyanogenMod is also based on AOSP) Rom-Developers tend to use an existing ROM like AOKP or Cyanogen as base because it's already compatible with a lot of devices. Porting "vanilla" AOSP is quite difficult and time-consuming because it lack's drivers and phone-specific code.