Jesus, there are a shamefully large number of man-purses in this thread. If you're going to have a messenger bag, get one with a wide strap, rectangular in shape, brown or black in colour, no handles like a woman's shopping tote, and large enough to hold at least a letter size file folder. Anything else screams vagina. See how it's done (taken just now):


Second pic true to colour. EDIT: Also, don't wear it over one shoulder, Christ Almighty.