I like laser etching bizarre materials and the latest is compressed cellulose sponge, which can be found at most craft supply stores.
Emulating a fantastic lawyer from a classically elegant television show, The Simpsons, I made sponge business cards.
Compressed sponges expand when you put them in water, its awesome! They were cut on a 35 watt laser at 100% speed, 100% power, and a frequency of 1000.
You can pick up some of your own on Etsy. They’re super fun to play with. Oh, I guess you could use them for cleaning too. I did a whole bunch of tests with sponges, with full details at kellbot.com.