Depends on the day of the week..

Everyday items:
* My phablet (Samsung Galaxy Note I)
* Wallet
* Glasses (in case)
* Two sets of keys: work which I need easy access to because of the garage door opener, and home which I need to stash somewhere safely.
* raingear in a neat small pouch.
* other miscellaneous items such as papers, usb sticks, occasional snacks, etc.

Mondays & Fridays:
All of the above, please clothes (two pairs of trousers, and 2-3 shirts & socks), plus some deodorants and cologne.

What I would like in a pannier would be some smart pockets, especially a phone pocket situated on the front of the pannier (towards the handlebars), and ideally a pocket with lanyard attaching point next to the forward facing phone pocket where I can have a set of keys. Also, all panniers MUST have a little loop on the rear where added lights can be clipped on.

Edit: Also, nice if the panniers halves are separated BUT have the ability to connect to each other so they can be carried away.