Are we talking me, IRL, thrust into the setting, or are we talking some power fantasy version of myself within the setting, with a sociopath's morality? Because those are two very different answers.
If it's the former? SAFE, Analysis Branch. I find them to be the least morally objectionable of the lot.
If it's the latter? Death Commandos or Light of Mankind, that probably gets pretty wild in way that would probably be fun if you're an adrenaline junkie with no conscience. Plus a decent chance of getting to jock a 'Mech.