MAC Pro Longwear Lipstain Markers.
They just give you the perfect hint of long wearing matte colour- colour which is more of a 'stain' effect as opposed to hardcore colour. It feels seriously odd to be using a marker on your lips, but it's kind of fun at the same time!
I'm devastated that they were discontinued (maybe because the name was too long?!)
So far Givenchy, seems to have come up with the best alternative to the MAC version but if you're looking for a more purse friendly alternative, Topshop does some great lipstain markers too.