There are many slivers within the definitions of "trope" that bunch some boxers. Jeffe & James have already reviewed them. On the positive side, I am particularly fond of how WriteWorld carves up the differences among stereotype, archetype, and trope. Their definition of trope is:
Tropes: Culturally-specific norms in storytelling. Tropes are cultural classifications of archetypes. There can be many tropes found under the umbrella of one archetype.
"Culturally-specific norms in storytelling." I love that. It makes me want to know more about tropes from around the world, particularly non-Western tropes. I also wonder if there is a hashtag or a thread out there in the Diversity in Fiction discussions focusing on culturally-unique tropes.
So, all that preamble aside, my 3 Favorite Fantasy Tropes are:
I do have a soft spot for the nothing-special kid who becomes a kickass wielder of magics. I like to read about the trials of their education, their screw-ups and the plot-changing repercussions of said screw-ups. Pug from Feist's Magician/Riftwar series and Hyacinthe from Carey's Kushiel series are examples. Yes, even Harry Potter, but Harry was a a bit too Chosen One for me. Imagine the story from Neville Longbottom's POV, eh?
2) The Artful Conjurer of Vengeance
Probably due to my deep, deep love for the classic The Count of Monte Cristo by Dumas (père), any story that holds my hand through the crafting of the perfect revenge--all meticulous detail of setting up the villains and watching them fall due to their own flaws--I wish I could find more of these.
3) The Human God
The protagonist begins the book as an every-man and ends the story on the threshold of becoming the deity known throughout history. The prequels of the Divine, if you will. What is not to love about the well-written seemingly plausible prequel? Epona, The Horse Goddess by Morgan Llywelyn and Red Branch (the stories of Cuchaulainn) also by Morgan Llywelyn.
There you have them, dear reader, my favorite fantasy tropes. If you have any recommendations, let me know!