I really like the Beauty Counter Touch Up Skin Concealer Pen. It's a clean beauty company, which is always a good starting point. The click-to-dispense brush pen ensures you don't waste it and makes application easy. They come in a range of skin tones that works for my dark skin, and it always seems to hide the dark spots without looking cakey. You can blend with your fingers and wear it solo or add a foundation or tinted moisturizer on top for extra coverage. I'm not a big make-up buff, but this product makes me feel like I may have stumbled into knowing what I'm doing.
My favorite combo right now is the Ole Henrickson under eye brightening cream and Nars Radiant Creamy concealer. The brightening cream has such a great texture for a base under makeup and helps to brighten and moisturize. The Nars concealer is a classic but lays so well over the top of this eye cream that they're my new holy-grail duo under-eye super hero stack :D