Ad Mediation

Hey all. I was just wondering what the best ad mediation tool is in 2016. Anyone have any suggestions?

I just started to use MoPub yesterday. My account is still under review and I need to submit admin page screenshots to prove the apps belong to me. In addition, I could not get my Admob ads to show up via the adapter. No runtime error or whatsoever, just unable to get ads from Admob. Still trying to fix this issue. Might use Admob mediation if I still cannot get it to work.