What would happen if an astronaut took his/her glove off in space but had the rest of their body completely sealed off?
My guess is that the hand would start to boil or freeze depending on location.
Without a glove, a space suit would basically lose its integrity. It is like not wearing a suit in the first place. Then, the question is what happens next.
The closest known resemblance of such a scenario happened during a test of an Apollo space suit in a vacuum chamber:(In 1965, a tube pressurising a space suit of a test subject, a man inside an evacuated vacuum chamber, had become disconnected from the suit by accident. Essentially without any pressure on his body, he lost consciousness within about 14 seconds, while he was still able to notice fluids on the tip of his tongue starting to boil before passing out. Because the chamber could be re-pressurized to a safe level within a total of about 25 seconds, this accounts for one of the rare cases in which a human being has survived such an incident without obvious damage.)
There is also a very nice video explaining what would happen to a human body in empty space:(It is the best and shortest explanation that I know of. It's worth watching it.)
A bit more reading with less chance of being taken off-line: https://web.archive.org/web/20140326132000/http://imagine.gsfc.nasa.gov/docs/ask_astro/answers/970603.html
It depends how suit is built. And in fact pretty similar thing happend to Joe Kittinger during his (>50 years long standing before it was recently beaten by Baugartner during Redbull Stratos flight) record jump flight from the stratosphere.
Kittinger lost pressurization in one of his gloves while still rising to altitude. He could abort the mission but he pressed on even as he lost feeling of his hand. The pressure outside was pretty close to vacuum (from PoV of human body everything above ~20km (or 12.5 miles) is like vacuum since boiling point of water falls below body temperature). After the jump he could not feel nor control his hand for a short period of time, the hand was considerably swollen, yet after a few hours it returned to mostly normal condition.