Captivate and Vibrant
Carriers: AT&T (Captivate) and T-Mobile (Vibrant)
Original OS: Android 2.1 ("Eclair")
Officially supported by CyanogenMod 9 community
Underneath their housings, these are essentially the same phone. Both come with a version of the Android OS that's so old most probably don't know or can't recall its codename. Yet these phones feature a pretty large screen at 4 inches, and 1GHz processor. You can install CyanogenMod 7 on the Captivate and Vibrant already, and you'll be able to use an official port of CyanogenMod 9 on them.