I have the 2, 4, and 5 (touch).
I also have a 3rd generation nano (which I think was my first iPod ever).
I use the 2 as a backup for my music and Bloons TD (it's only 8 GB)
I don't use the 4 much, but it's usually for Clash of Clans and messing around with jailbreak tweaks
I have the 5 pretty much set up with the same stuff I have on my phone. It's sort of like my "backup" device. I use for media consumption and casual games (it can't handle much). I also use it to get apps that my iPhone can't hold (iWork and iLife bundle).
The nano sits on my desk. It's pretty cool to display because it was my first iPod ever. By the way, it still works pretty well.
I also had an iPod nano (not sure what model) that I lost
I say that the 2 is slow but pretty cool to own, the 4 is a lot better than the 2 but can't really hold a charge, and the 5 was awesome on iOS 7, but iOS 8 slowed it down big time.
They are still quality devices, and I'm glad I still own them!