If you don't have a huge budget, get a used Nexus One off of Craigslist for 2.3 compatibility, and either a Nexus 4 ($299) or a Nexus 7 ($229) for 4.3 compatibi

If you don't have a huge budget, get a used Nexus One off of Craigslist for 2.3 compatibility, and either a Nexus 4 ($299) or a Nexus 7 ($229) for 4.3 compatibility. That will depend whether you need to test your app on tablets. Another option for 2.3 if you want something new is the Samsung Galaxy Player - there's a whole line of these, but they have no phone functionality.