Washers come in all sorts of sizes, inside and out, so they make pretty good on-the-fly tokens in my opinion.
If you simply need the tokens to be faceless counters, then you can stick with the plain old washers themselves, generally using the smaller ones to save space.
If you plan to have pictures on the tokens, try to find the ones with the smallest hole, or inner diameter, with the outer diameter of your choosing. Then it'll cause less interference later. Then you can print (or paint or draw - whatever you'd like) the picture onto a piece of paper, cut out the circle and glue it onto the washer. I recommend super glue; you don't need much, and I have yet to see any of my tokens come apart after several months of use. Although, if you use super glue, you must use cardstock or other thicker paper because super glue bleeds through normal print paper.
My favorite part about these tokens? They match these 6-sided dice made out of bolt nuts! Maybe you can make pawns from nails, screws, or bolts (ooh, that's an idea I might have to steal...).