I think this question would be different if you specified that we could only use a single ester of test or if we have unlimited access to all esters of test. Having all esters of test at my disposal I would probably choose a short/mid ester compound to blast with. As many of us age, we realize that you really don't need much else besides test unless you compete. So, for me it woudl be between Tren Acetate, Primo DiPropionate (or acetate), and NPP. Being that I have no intention of competing and would like something with little side effects as I age, I'd have to say Primo as well.