I don't think of myself as being particularly sentimental, but it really melts my heart when kids make stuff for me at work. Student artwork is really the sweetest thing. You know kids never really have money, and so their little offerings of cut up paper, crayon and marker are their most sincere, humble tokens of appreciation.
Over the last couple of years, I've collected paper flowers, colored hearts, various animals doodled on notebook paper, and lots of "I Love You, Ms. C!" notes. Designs, pictures and notes that are cutely decorated and usually pretty simple (and, to my amusement, often misspelled). Little girls make things like this all the time. Most elementary classrooms I visit have tons of this stuff near the teacher's area, which shows I'm not the only one who values student gifts. Nice to know you can touch a student just by getting to know them for one day. Since I've started, I've probably collected dozens of things here and there.
And I've saved every last one.