IO Interactive recently brought back Hitman 2's briefcase bug (opens in new tab), which turned briefcases into gently spinning homing missiles, as an unlockable weapon. It is simultaneously crap and brilliant, always finding its target... eventually. Now that it's in the game, you can take it for a spin yourself, but first a video demonstration!
D-ClassPersonnel posted a two minute clip (opens in new tab) on Reddit showcasing the briefcase's many wonderful features as it slowly—very, very slowly—hurtles towards its jogging target. There's a lot to enjoy.
Unlike, say, a bullet, you can actually outrun the briefcase, but you'll have to keep running forever because it will never give up. Another person blocking its path? It will just pass right through them. Walls? Screw walls, it can pass through them as well. It's also extremely quiet, so nobody will notice it. Not even when it's clipping through their skull.
There's a point where it almost looks like it's catching up, but no, its target turns a corner and gap increases. It's not until she stops for a chat that the briefcase strikes. Honestly it would be a great incentive for my jogs, which I usually end after 1 minute, heaving up my guts and melting in a puddle of sweat.
If you want to kill in style, you can unlock it in the Best Case scenario, netting yourself the ICA Executive Briefcase MKII. It comes with a sticker.