Three iterations of the cutie mark that went into my derpy bag.
The third one is the latest and the one I actually used. I milled them from 3mm aluminum plate using a mini CNC router and tumbled them overnight (third one not yet tumbled in this picture) in a ad-hoc tumbler made from a cardboard tube, duct tape, a small electric motor and gravel as tumbling media. Worked better than expected.

Of course, after making these three, I noticed a mistake: the top left bubble (or bottom right as they appear to be upside down in this picture) should be on the right side. Oh well.