I'll third FO:E and its light-hearted spin-off Pink Eyes.JaceArveduin said:Dragonriders of Pern you say? I rather enjoyed those books, might have to take a peek at that.Fayathon said:It's an interesting crossover of a story and I've been enjoying it thus far: The Queen Who Fell to Earth [http://www.fanfiction.net/s/7591040/1/The_bQueen_b_bwho_b_bfell_b_to_bEarth_b#]
It's Harry Potter crossed with Dragonriders of Pern. It's one of those fics that doesn't sound like it'd work but it does, much akin to Fallout:Equestria.
Phew, this is a hard one, can't remember many that I've read, though I'll second FO:E and some of it's off shoots (from what I've read of Project Horizons, I'm actually liking it better)
Meh, can't remember any names, though I do remember reading this short lil fic about how "Twinkle" got its name (Drizzt) and it was hilarious. May not have been written well, but it was a fun read.
As for some other (MLP) fics I've remembered:
Heavenly Turmoil [http://www.equestriadaily.com/2011/10/story-heavenly-turmoil.html], which is a fantastically dark take on Discord and his somewhat chequered history.
It's Always Sunny In Fillydelphia [http://www.equestriadaily.com/2011/06/story-its-always-sunny-in-fillydelphia.html], which is one of the best ship-fics out there (it certainly doesn't overdo the shipping), and was one of the first MLP fan stories I read.
Elements Of Awesomery [http://www.equestriadaily.com/2011/07/story-elements-of-awesomery.html], which is one of those deliberately badly-written fanfics, and it is hilarious.
(Also, out of interest, how far into Project Horizons are you?)