Right now I'm using a Hayden-Harnett flight tote thanks to the vicious winter weather-- in the summer I use a Balenciaga Part-time or a YSL Muse 2 depending on how much stuff I have to carry. Personally I like the style of the Muse 2 better but the Balenciaga holds more files/folders/etc and is better as a business travel tote.
I have a Gucci tote I like to use for work papers and/or laptop. It's the GG material, so weather is not a problem and the handles are perfect for shoulder OR arm. Right in that perfect middle ground.
I've had to move from shoulder to arm due to neck/shoulder problems, so I usually carry my Lindy with my "purse stuff" and the tote.
Usually a LeSportsac Tote but lately I've been using a HH for Target canvas bag. I don't like to bring nice leather purses to work because we've had things stolen from even locked offices, plus I work in a hospital (which I consider all areas to be dirty).
An ABRO caramel leather backpack--I work at a University in student services, though, so a backpack isn't too casual (not like I'd care even it it were, really--I've been a shirt-and-jeans chick for about 35 years now).