Well yes, Greenknight gets his head lobed off, but he then puts it back on. The scary part is that in a year's time he'll get to return the favor (but doesn't, because it was a test of chivalry (and the protagonist was chivalrous)). Wikipedia has a synopsis.
Sure, but Gawain only finds that it's a test after the fact (by surviving the test due to his virtuousness). So my take away was always something along the lines of don't play games whose stakes you may not fully understand against people whose power you may not fully appreciate especially if it doesn't seem like there is a downside.
