As a comp sci major who tries to avoid greasy/crumbly/etc food and snacks, this is a topic I always come to. I try to stay away from cookies/chips/trail mix because of crumbs.

And as a fan of Japan (and having local Japanese markets around), I like to pick up some japanese snacks. And they work so perfectly because Japan has that same ideology. Hi-Chew is really good. It's like a mix between starbursts and gum. Quiet, not messy, chewy, and tastes good. And unlike gum you can just swallow it once you are done. The downside is the amount of wrappers the snack leaves behind. They come in packs of 10, and each are individually wrapped as well.

I also like Pocky as a snack. They are pretzel sticks with a chocolate coating. The ends are left uncoated so you can hold them without getting chocolate on your hands. They are decently clean, still a bit crumbly though (not as bad as chips). They taste great (who doesn't like chocolate?) and they come in a few packs contained in a box. Or you can just buy the packs individually. The only problem is that they don't really last a long time.