Most people won't ever find a need for this BUT if you do- its good to know.
When I was teaching I had a toner cartridge that the copier wouldn't recognize for some reason but it still had quite a bit of ink left it. It wasn't until recently that I found out a way to get it out with one of the thousand syringes we have at our house. I attached it to the end of the ink reservoir, turned the ink down, and pulled the ink from the barrel with the suction of the syringe. I filled up an old jar full of this gel ink and I barely made a dent in the cartridge. So I have lots of ink to play with!
I even squeezed some onto an old ink pad and it works great as a distress edger. I can stamp with it but the images come out a little blurred.
NOTE: this is a resin based ink that is flammable and should be used in a well ventilated area. Avoid breathing in chemicals.