My favorite has always been Apple Lane, specifically the Rainbow Caverns. Griffon Mountain is really nice, but I've never really been able make good use of it. Part of the problem for me is that the region really isn't a good place for Cults of Prax types to go if you're really into the training and cult benefits rules - not enough presence of the cults to get good training.
But part of the problem is also that I'm not much of one for epic adventures. My gaming ADD gets in the way :-)
What is the best rq adventure in most people minds? Griffin mountain
Griffin Mountain tends to be what most people say, although it's really more of a complete campaign than an adventure. Both Apple Lane and Snakepipe Hollow are both closer to traditional adventure modules and really highlight the differences between RQ and other fantasy RPGs, especially D&D.
I'm refereeing Apple Lane on my board, Gringle's Pawnshop, at the moment. It's been so long since I last played it that I don't really remember it too well but I'm having fun with it at the moment. I did referee Snakepipe Hollow once and had lots of fun with that too.
I did enjoy Griffin Mountain back in the day and I'm currently involved in a Balazaring adventure through a Yahoo group.
However I think my favourite has to be Pavis and the Big Rubble with occasional forays into Borderlands. I would be happy indeed if I could get my hands on those.