My game-changers over the past couple of years have all been environmental (moving across the country, having a child, and moving back across the country). My wardrobe is still struggling to catch up...
I'd say ankle boots have been a game changer for me (along with limiting my shoe purchases to minimalist styles):
http://www.softstarshoes.com/a.....rrant.html
I never really jumped on the tall-boot bandwagon, since I've never had the critical mass of skinny pants to justify it, although I do keep a pair of tall boots around for wearing with skirts and dresses. Ankle boots, though, make so much sense for the type of pants I like to wear -- cuffed/cropped, sometimes a bootcut or straight leg.
I wore through two pairs of higher-shaft lace-up boots (more combat style than chukka style) in the past year or so, and once I got rid of them I realized what a major role they played for me. The low-cut boot is even more versatile for me right now, though I am thinking of adding another taller pair in the future.