What kind of bag do you use for your carry-on?  

I have one of those messenger style ones that can be strapped/attached to my luggage handle. I tend not to have a lot with me going onto the plane. I never considered a backpack though. 

I just have a small tech bag. I am not really sure what you would call it. It isn't a backpack or a crossbody bag, more like a man's purse I guess one could say. 

I use a backpack of sorts as well. It is like one of those college type ones with lots of compartments so I can stay organized on the plane. 

I use a cross body bag. Not really sure what it actual style is called. I guess you could consider it just a messenger bag. I used to use a backpack but I tend not to have as much on me when I travel now that I am older. 

I have what I consider to be an over-sized pure, really. It is a tote bag but has a lot of compartments and spaces. It is so large, I can carry my standard pure inside it with plenty of spare room.