I'd want my purple death paly colony to triple in size, my green cactus coral to finish covering the big archway rock, and my LTA to go *poof* and turn into a bright green BTA. If a big ol' starry blenny and 5 lyretail anthias appeared in my tank, that'd be great. And if it wasn't too much trouble, I'd also like him to wave a magic wand and create a reef safe panther grouper.
Other than that, not much.