So, an orc, a wizard, and a dryad walk into a tavern...
Hang on. Fantasy, that's funny? Surely not. Isn't fantasy all that one-ring-to-bind-them and winter-is-coming and complete-this-mythical-quest-or-the-demon-warlock-king-of-Evilsbane-will-curse-your-firstborn stuff?
Well, yeah. But it's a whole lot more than that. It's rodents-of-unusual-size and it's anthropomorphic biscuits called Gingy and it's "Truth! Freedom! Justice! And a hard-boiled egg!" as well.
Of course, fantasy can be funny. With an author's palette limited by nothing more than their imagination, fantasy can be anything. Look no further than the contents of this guide for evidence of that.
And as with any genre, a story of complete and unrelenting seriousness would make for pretty grim reading. Whether it be as broad as the Silver Sea or darker than dragon glass, there's humour to be found in most fantasy, even if you might need to dig a little to locate it. The RRs (Tolkien and Martin, of course—try to keep up) are hardly known as the genre's premier chuckle-meisters, yet the hobbits of the Shire are usually good for a little comic relief, and Tyrion Lannister is a dab hand with the witty quips.
Which begs the question, where is the line? If there's at least a modicum of humour in almost all fantastic tales, at what point does the comedic content make the story a comedy? When does a funny fantasy become a fantastical funny? Where's the cut-off?
And the answer, of course, is there isn't one. There's no line, with serious on one side and side-splitting on the other, and never the twain shall meet. Instead, there's a spectrum—fluff and fun at one end and despair and darkness at the other, with a glorious, mashed-up, multitudinous gamut betwixt the two.
Up towards the more fun end of things you'll find works by Tom Holt, Ben Aaronovitch (way to get pole position on the bookstore shelf there, Ben), Jasper Fforde (nice try, Jasper, but Fs aren't going to cut it), Neil Gaiman and Robert Rankin, plus a host of others. Far more than I can name here, however encyclopaedic lists to peruse at your leisure are a mere google or Goodreads search away. The range of humorous fantasy is vast and varied—just like fantasy itself.
And within that range, of course, lurks the undisputed master of otherworldly chuckles—the genius (and now sadly deceased) Sir Terry Pratchett.