Basically, people who think the government staged the Sandy Hook shooting in order to pass more gun control.
I of course think these people are idiots who believe everything is a conspiracy theory. They have so far as to post the phone number and home address of a man who sheltered frightened children and a bus driver in his home.
This article right here pretty much disproves all their claims.
http://www.snopes.com/politics/guns/newtown.asp#hoax
... and they apparently decided to start out as low as the could:
http://newsfeed.time.com/2013/01/16/sandy-hook-hero-harassed-by-burgeoning-truther-movement/