It looks as if Joan Rivers is about to go, which is unfortunate. She was an utterly fearless comedian. She was sharp, and unafraid to be offensive, and stayed that way right up until the day she went into a coma.
The best tribute I can give her is simply to link some of her standup acts.
This is about nine minutes from a 2010 documentary about her called Piece of Work, which shows how ferocious she was. At about the four minute mark she does a wonderful job of facing down a heckler in Wisconsin, actually working in a little humor while doing so. The clip also shows her offstage, and you get a sense of how tough she is.
Here she is in Live at the Apollo, Part I and Part II. Some of what you'll see here is regular old-timey schtick, but her nerve and timing and humor are faultless.
Rivers was the anti-Robin Williams. She was iconoclastic, disrespectful, profane, scathingly sarcastic, and almost always on target.
The fact is, you can't be funny if you're not those things. (Who was the last politically correct person you met who was truly funny?)
Rivers was -- along with Kathy Griffin -- one of the two best female comedians I've ever seen.
Addendum, next day: Rivers died a few hours after I put up this post. RIP.