Nitrous Oxide

great stuff heres the ebay guys i bought mine from...

http://tinyurl.com/zzmvn

thats the "cracker" you will need to harvest the gas from the cartridges...

http://tinyurl.com/jevlr

thats the cartridges... you will also need baloons you should prefer the ones with rubber bands on them punch baloons i think...

safe secure and totally awesome...