My current favorite is the Essence Cover Stick concealer.
The concealer stick comes in a little twist tube about the size of your average lip balm or lipstick, which makes easy to stick in your bag or purse to carry around all day. The packaging the concealer stick comes in is pretty minimal, which I appreciate so I'm not creating so much garbage that will go into the environment.
The consistency is solid enough that it's easy to build coverage on especially dark blemishes, but also creamy enough that it is easy to blend out so you can avoid having little cakey mounds on your face. I much prefer this over concealer sticks that don't seem to be doing their job no matter how many passes you make over a particularly dark blemishes.
Unfortunately, Essence now only has two shades of this particular line of concealer stick that I'm aware of: Matt Honey (03) and True Nude (04). I believe there used to be at least two more, but I can't find any trace of them on their website.
The Matt Honey color seems to work well with my skin tone, which is a pale olive color. In fact, the color matches so well to my skin sometimes it's hard to see the concealer is there even before I've blended it out.
I have also never experienced any adverse reactions or breakouts since from using this concealer stick, which is also of course, a huge plus.
The price of this concealer stick is extremely affordable at only US$3.00. This of course will vary depending on what country you buy it in.
How long a stick will last you really depends on how often you're using it, but I use it basically every day to cover dark circles under my eyes and blemishes (and I sometimes even use it as face contouring highlighter!), and it still lasts me several weeks.
Not all countries carry this brand, so check out their website to see if there's one near you, or simply find Essence Cosmetics online.