Screed:
Thanks, but to clarify, I wasn't asking about a disarm as the gentleman is not armed. He just has weapons on his body, not in his hands. Being invisible, what would I need to do to walk up to him and take a katana out of its sheath or a gun out of a holster?
Currently, you are in broad daylight, so you must first approach when he is distract with something else (such as fighting your teammates). You must start outside the line of sight before moving in.
Then:
1 - Contest of Skills (Invisibility Art vs. Vision roll) (to make sure he is not noticed)
2 - Pickpocket or Sleight of Hand-4 or DX-6
3 - For good fighters (i.e. those wary in combat) you must then make a Contest of SKills (IQ vs. Pickpocket skill roll in 2). He gets modification for Alertness. If he has Streetwise, he uses that instead of IQ.
If you have something else similar to pickpocket or sleight of hand, then I will consider using that number instead.