I tried it and it works but it's temporary. ;D I inhaled one at a party yesterday, it was so hilarious. LOL!
Watch this!
http://www.youtube.com/watch?v=d-XbjFn3aqE
MTF - Helium
http://www.youtube.com/watch?v=M7y8mCHrDxU
FTM - SULFUR HEXAFLUORIDE
http://www.youtube.com/watch?v=XzT2Xqp1Q5Y
Oh no! haha apparently that's really bad for your throat though...