It's a gas.

[vakkotaur]

Sure, I've seen the foods list. It had a few drinks in it as well. But that's just two phases of matter, solid and liquid. This will help to complete the set. This is not a list of things you should try. There are some gases that are very much not recommended.



I might be wrong about a couple things, but what I can recall, I've marked.

Bold gases you've breathed.
Italicize gases you've only caught a whiff of (even if odorless).

Hydrogen
Helium
Neon
Argon*
Krypton
Xenon
Radon
Fluorine
Chlorine
Bromine vapor
Nitrogen*
Oxygen*
Carbon Monoxide
Carbon Dioxide*
Water Vapor*
Nitric Oxide
Nitrogen Dioxide
Chloroform
Cyclopropane
Diethyl Ether
Ethyl or Methyl Mercaptan
Halothane/Fluothane
Isoflurane
Nitrous Oxide
Ozone
Acetone vapor
Acetylene
Ammonia
Methanol
Ethanol
Butanol
Sulfur Dioxide
Hydrogen Sulfide
1,1,1-trichloroethane
2-Chlorobenzalmalononitrile (CS tear gas)**
Carbon Tetrachloride vapor
Arsine
Chlorine Trifluoride
Hydrogen Cyanide
Phosgene
Silane
Selenium Hexafluoride
Sulfur hexafluoride
Uranium Hexafluoride

* Atmospheric
** Actually delivered as an aerosol and not as a true gas.