Mainly just surfing the web, checking my email, use it sometimes to take lecture notes using Pages or Notes, reading ebooks for class, and of course playing games and youtube
Games.
Netflix with Airplay on (so I select what I want on iPad and play it on TV).
Remote app with Home Sharing (select my music from my Mac and play it on my entertainment system)
Browsing & email.
My iPad 3 is no longer my primary tablet, but my usage hasn't changed. I use my iPad to create basic Pages documents for work as well as Numbers and Keynote. I have my work and personal email synced. Sometimes I watch a move or TV show I purchased on iTunes via iTunes in the cloud. Business wise the iPad is the best because everything is on iCloud, so everything I write during work is automatically on my iPad after work. During college I used my iPad for social media and a bit of Clash Of Clans.
My Nexus 6 is an incredibly fast, stable and reliable smartphone I use for heavy multitasking which is big part of my workflow. It's easy access fully functional file system accommodates many of the files from my laptop, so when traveling for business as I often do I load it with my laptop files which I can review and edit while on the plane between destinations.
It's 6" display is terrific for Video and TV at the end of my work day. My iPad Mini is used similarly.
I carry my iPhone 6 Plus as my secondary / backup iPhone which comes in very handy to use for variety or if something happens to my primary phone. They both have their strengths and I enjoy the combination.