Tom Stoppard wrote it in 1966. I loved it. I loved it not just for the clever way that the playwright inserted his characters' point of view into the story, using a sort of theatrical kaleidoscope that showed something completely different (a technique used in later plays like Wicked) when the view shifted, but also for the language. R&G is very much a play about language. The play is full of quotable lines--"Who is the English king?" Rosencrantz asks. "That depends on when we get there," Guildenstern responds. The Player has a great speech about the kind of entertainment he and his players provide, offering up love, blood and rhetoric in various combinatins, but always with blood. ("The blood is compulsory," he says.)
The movie is currently streaming live on Netflix, or you can buy it used from Amazon for less than $5.
This play isn't the only time that Stoppard has fiddled around with Hamlet. He has also written Dogg's Hamlet and Cahoot's Macbeth, two plays meant to be performed together, Dogg's Hamlet plays with language also (in a way that will remind Stoppard fans of his play Travesties) and Cahoot's Macbeth is a shortened, stylized version of "the Scottish play."
Stoppard also wrote The 15-Minute Hamlet, which is exactly what it sounds like, the entire play reduced to 15 minutes. You can catch all kinds of performances of this play on YouTube, The version you won't want to miss is the two-part, short-film adaptation that stars Austin Pendleton as Hamlet, Philip Seymour Hoffman as Laertes, and Xander Berkeley as Shakespeare. Here's the link to part 1. Here's the link to part 2. The filmmaker is having a really good time sending up Hollywood filmmaking, which adds an extra layer of playfulness.