Metagross. 130 Def and Steel resistance means it can take bullets like a boss. Psychic powers and the strength to bring down any building help too. Bullet Punch would help in hostage situations. Plus, it's super intelligent, so it can figure out the criminal's plots effortlessly. I'd just be its sidekick by picking up important objects, pretty much.
Alternatively, Rotom. It's a ghost, so it can't die, plus the ability to ambush people by just turning into an appliance and zapping them has to be useful.
Why do I have to move with the crowd of kids that hardly notice I'm around? I work myself to death just to fit in.