Gain is such a beast...what type of music will you playing? Or what type of gain are you going for?

Reverb: Yet another beast...you could fill a dictionary with differnt types of reverb. Here's a list of high quality reverb pedals:

Danelectro Spring King Reverb

Electro Harmonix Holy Grail

If you want to go rack mount I'd use the Lexicon PCM reverb.