I bought these pens...a cute, little, fine-tipped rainbow...the entire package of eighteen pens is only 5 inches by 6 inches.
This is good because my school bag pretty much ends up as a traveling office. I try to pack it efficiently with everything I need, but not a single item more (otherwise it's an awfully cumbersome traveling office).
One of my (too many) ideas for next semester will have me initialing a heck of a lot of student work each day, therefore I decided a tiny, colorful array of initialing choices earns a spot in the bag.
Oh and this is my bag, which is actually my mom's bag that she let me borrow...three semesters ago.