Sandstorm, because I am a Dark Sun nut and the climate and terrain rules in there are great. Spells and feats are cool too, as are some of the sites. Prestige classes and monsters need a bit more work, but ya gotta love a giant cactal treant.
My favorite dessert is cheesecake. I'll wait for the pies and pastries sourcebook, Sugarbuzz. I've been waiting for more rules to add to an "Orc and Pie" campaign. Especially an expansion of the Profession (cook) rules!