If you prefer the feel of writing or sketching with a freshly sharpened pencil and are fastidious about keeping hydrated, this clever piece of synergy is going to blow your mind. Designed for use on standard plastic water bottles, this pencil sharpening bottle cap is a brilliantly obvious way to deal with pencil shavings.
It all but guarantees the shavings are not going to spill as long as the sharpener is screwed on tight, and you probably don't have to empty the bottle for months on end — depending on your pencil usage. It just might be the best $3 you ever spend, unless you just opt for a cheap mechanical pencil that never needs sharpening. But where's the fun in that? Shachihata via Fancy]