Everyone who uses after run oil has their favorite. Here are a few I've seen recommended:

ATF: any brand but not 'Type F'
Full Synthetic Motor Oil: Mobil 1, Castrol Syntec, etc. The recommendations are usually a low viscosity like 0W-30 or 5W-30
Air Tool Oil: Marvel brand is popular but any brand is fine
Half ATF & half Marvel Mystery Oil (which is different than Marvel Air Tool Oil)