hey hey.
ive used liquid karma with pretty good results and lots of people around here swear by it. it definitely produces a more vigorous plant.
cal mag plus seems to also work well. i use it every once in a while to keep everything in line and ive never had any cal or mg problems.
gravity is a flower hardener and finisher made by humboldts own. ive used it a couple times and it definitely does pretty much what it says its going to do on the bottle. it can make rockhard nuggets which isnt always desirable, so be sure to follow directions and even use less than the recommended amount.