I regret buying:
*the Real Techniques Eye Collection Set. These are amazing brushes. A.MAZING. However, out of FIVE brushes, I use ONE every day. I haven't even used two of them (at all) and I purchased this set about five months ago.
* Every face primer I own. Neutrogena Shine Control. Boots No. 7 Beautifully Matte. I still end up looking like an oil slick by the end of the day. I'm currently testing MAC's Oil Control Lotion but my hopes aren't very high.