My two big disappointments at least didn't cost me much-- this is not to say they were both disappointments because they were cheap, though.
The first was the free little MUFE mini lipstick that came as part of Sephora's birthday gift. It didn't last long on me, and I wasn't a huge fan of the look or the feel. The 'universally flattering' color was okay on me until it started to wear off and the color it wore away to was just not a good one for me. So, brand that I'd only ever heard good things about, solid reputation, way up there at my own personal high end, in terms of what's in my beauty bag... but just not working for me. But since I didn't spend money on it, I can't really complain.
And then the second was a super inexpensive product. I couldn't find one of my traincases one day and it was the one that had my favorite foundation, so my solution was obvious-- buy a second foundation-type product to keep in my other case, so that no matter which I had on hand (either because of traveling or because of moving/cleaning/what have you), but I didn't want to blow a bunch of money when I knew that if I'd had time the other day, I'd have gotten to my foundation eventually and that it's still good and more full than empty.
So I bought a super-cheap BB cream from N.Y.C., and... meh.
I don't HATE it? My sister says it looks good on me, but I really want fuller coverage than it gives, and it does not cover up my big redness problem. I don't mind people knowing my face tends to be blotchy and red, there are plenty of days when I'm not going anywhere where I feel the need for a full face of makeup, my sensitivity over my face is pretty limited to my literal skin sensitivity... but when I do put on a liquid face product, unless it's just a tinted moisturizer, I do want that redness to be gone. The BB cream evened me out a little but I could still see more redness than I like. The tone was also too warm for me, so while it's better than nothing and I'll totally use up the tube because it blends smoothly and doesn't look cakey after a while of wearing it, I'm just not a fan of how it makes my skin look not quite right. (it's hard to find one that is right because without the red blotches, my natural skintone falls somewhere between 'deathly pallor' and 'translucent')