Heh, you should try this one. I call it
the heart-attack thing and I've done it on IRC a few times. Not only is this advised by medical professionals as being potentially fatal, but it's also a good way to kill time if you're bored.
On thing I would suggest, however, is not doing it too often. I usually leave a few weeks in between "sessions". Also, if you have any heart conditions or are prone to falling unconscious/into coma, then this might not be the best idea for you.
- Find an open place, preferably with a solid wall at your back, or a soft carpet to fall onto.
- Crouch down in a fashion similar to how you would sit if you were planning to relieve yourself in a forest.
- Breathe in deeply 20 times and breathe out after each time, retaining the crouching position as you breathe. Adjust dosage if desired, but with caution.
- As soon as you've finished, stand up quickly, put your thumb in your mouth, closing your mouth around it, and blow hard on it.
- ???
- PROFIT!
And no, I wasn't just using that format for its questionable presentational value - those last two steps are literally what you should feel like after coming out of the drooling stupor you will find yourself it. You may also feel slightly cold and numb along your extremities and especially in your brain, but this should be harmless as I've done it three times without injury.
This should make you feel inert, confused, euphoric and thrilled all at once, but I cannot say what it may feel like to any individual person. The only way to find out is to try it.