What type of tool do I need for this screw holding my license plate?
This is secure hex bit or similar. There are a bunch of varieties. The basic idea is to take a "normal" head (e.g., a standard hex or Torx) and add something to prevent the regular bits from working. It is of limited use as far as real security because the bits are usually not hard to find. For example, this set from Harbor Freight or this set from Home Depot. Search for "security bit" or "tamper proof bit" or similar.