Definitely concealer, eyeliner (pencil), blush and lipsaver. But if had to choose only one it would be concealer all over my lids (instead of eye primer) and under my eyes. It really awakes my whole face and makes your eyes pop. I love my Maybelline Affinitone concealer in shade 1. I have a review on my blog about this concealer Love, love, love it and the best part is that it is cheap and has no strong scent.
*edited by mod: blog link in post*