You vs Harry Potter
Location: Time Square
Scenario 1: How many hours of prep do you need before you are dropped into a fight with Potter?
Scenario 2: You can't use guns and have no money for prep.
This is Potter from the Seventh movie. He can only use feats he did on-screen. Example: He cannot use Avada Kadava, because he didn't do it on-screen. Potter cannot run away via apparition (or apparate away to get something), he needs to stay in the area. Standard equipment ONLY. No Luck potion or Invisibility cloak. No goddamn hall of prophecies bullshit or anything similar. Potter gets absolutely no prep whatsoever. End of discussion. When you decide to start the fight you are both apparated to the centre of the Square, 10 metres apart. This is not to say that you cannot set up prep in the Square itself. In fact, this is in the spirit of the thread.
Have fun and try to get creative. Really creative stuff will get you an internets cookie.