I am giving myself an iPod touch for Christmas. I have been wavering because it is such a duplicative device. However for me, it boiled down to filling gaps in my daily routine.
For example, I cut cable a long time ago but I still love to airplay TONS of "channels" from my iPhone to my 64gb Apple TV. There are quite a few apps not natively available on the Apple TV such as SyFy, Discovery GO, MSNBC, FoxNews, AMC, etc. I don't like using my iPhone for this because it basically disables the ability to use it for anything else (web browsing, taking a call, texting, etc.) It also drains the battery too, especially since many of the apps mess up when you airplay something and your phone goes to sleep 1 minute into the show. This way I can airplay my show, plug the touch into an outlet (turn the auto-lock off), and multitask on my phone while my show plays.
The second reason I am opting for an iPod touch in addition to my iPhone is for podcasts and music while at the gym. My iPhone 6Plus is only a 16gb phone, and therefore I can't store any of my music locally on it. Once I have the iPod touch, I can save all of my music to it and throw it in my pocket while I work out. In addition, I can create multiple playlists from my apple music subscription and save it for offline playback, saving me from the occasional large cell phone bill.
The third reason is portability. I love the 4 inch screen and how easily it fits into my pocket, especially compared to the beast that is the iPhone 6Plus. I love that big screen and it's perfect for playing games, browsing the web, etc., but with all the extra screen real estate comes a lot of compromise in portability. The iPod touch works great almost everywhere I go during my normal routine. My gym has wifi so I can send and receive iMessages in case my wife or family member wants to contact me and my phone is in the locker.
All of those reasons combined is why I ultimately decided on an iPod touch. My wife "stole" the iPad and I thought I wouldn't miss it, but when most of your shows have to be airplay'd to the TV you start wishing for a second device. That got me thinking about portability, data overages from streaming so much of MY own music that I can't store locally, to little things like taking an iPod somewhere for the purpose of taking pictures or another basic use where I wouldn't want my more expensive iPhone to go.