I found this Weird Dice video interesting.
In Treasure Hunters Prolix, we only use six-siders. A lot of the mechanics are based on 2d6 or higher numbers of d6s.
Wouldn't it be really cool to put a couple-three nonstandard dice into ta RPG game box set? We could make up all kinds of weird tables and surprising arrays with some weird dice.
A d4 + d9? Cool! Or a set of Sicherman Dice?
There's a lot of places where you can buy weird dice (for example), but is there anywhere you can get custom dice for cheap?