The Yeti Pot and its more famous cousin the Neti Pot are amazing little guys. Mostly used for flushing the nasal and sinus cavities.
You mix up a pack of "Schnoz" wash, with some warm water, tilt your head to the side, insert the spout and begin flushing. Now your very first instinct is going to be to block the water coming into your nose, or to swallow. But you just allow the fluid to flow into the passageway and drain out of the other nostril. This is really good for infections or blocked air ways due to cold or allergies.
As the Dr's say, it is very healthy and very safe, if used properly. The benefits far outweigh the "possible" risks. Now I am not a doctor or a medical professional, and advise you to speak with your doctor or healthcare provider before utilizing one of these devices.
It is a really weird experience the first couple of times when using it. I use bottled water when I use mine. Just because I know what type of chemicals my municipal water has in it, and I dont want chlorine and bleach in my nose. But it really is kinda "fun" in a disgusting way lol.