Continuing a refillable things theme, I'll put in a plug for decent refillable pens.
Pens are the sort of everyday thing with which it's easy to get by indefinitely with cheap disposables whose use is a little frustrating. But, at not much of a premium, you can get a comfortable refillable pen that works much better. The Sanford PhD and Dr. Grip Gel are two models I like.
For either of these, a 2-pack of refills can be more expensive than a box of 12 of the cheapest ballpoint pens, so it's not clear that this is a cheaper path. But it's so much more pleasant to deal with a pen that's easy to hold, whose ink flows nicely, and which lasts a long while before needing a refill, that I find it worth it (and I'm happy to be generating less waste.)