Hah! I hate what I've come to refer to as "mirthless laughter." Especially when it's paired with feigned incredulity. You know, the way some people will mask their hostility with a fake little puff of air (or in more versatile mouths, a series of tiny exhalations), often accompanied by an eye roll, an insincere smile, a weary head shake, or an unconvincing "That's hilarious." And I also hate the way there seems to be no real word for it. Snorting is the best I can come up with, and that doesn't quite capture the phony amusement part. Maybe a French phrase is what's called for in this case. Something like rire sans joie. You'll often hear it in a court of law, when a witness is presented with some evidence or an accusation they clearly wish to deny. It's sort of like when people use the words honey or sweetheart as a putdown. It's like taking something that is only in the world to do good, and then poisoning or corrupting it. Or at the very least, kind of mussing it up. I'm not trying to be funny here, but we found three examples of Amusment* in OhioLINK today, and 72 in WorldCat.
(Announcement in a cafe in Oirschot, the Netherlands, September 2008, from Wikimedia Commons.)