I carry a Maxpedition Mongo everyday. It's messengerish as you can fit folders and stuff in the main compartment. But it's crazy versatile. I get a wild hair every once in a while and get some new bag or pack to EDC and I ALWAYS come back to my Mongo. Best bag I've ever owned. The only thing I don't like about it is the cell phone pouch permanently attached to it. I wished it just had a molle grid so I could choose what goes there. I up graded the large plastic buckles with aluminum ones and replaced the shoulder strap with seat belt style webbing as it's softer and more comfortable. Best bag ever though.
"If you can't take a little bloody nose maybe you ought to go back home and crawl under your bed. It's not safe out here. It's wondrous, with treasures to satiate desires both subtle and gross, but it's not for the timid."