The iPad 2 can be downgraded to iOS 6.1.3 or 8.4.1. Both offer better performance than iOS 9 and have untethered jailbreaks. Once downgraded and jailbroken you can sideload hours and hours worth of games. A lot from that era are IAP-free.
I use an iPhone 5 downgraded to iOS 6 (tethered) as an iPod. I love how I can unplug my headphones from my work Mac, plug directly into the phone (no adapter required!) and it effectively mutes Slack without actually muting it. Syncing with the latest version of iTunes still works, albeit slowly.
I also use an iPad 4 (tethered to iOS 6) as an ebook. iBooks works great and I love the pseudomorphic design.