I'm reminded of Pitch-o-mat 5000. The pitching robot from Futurama that was a modified howitzer. If you want to make a robot to do a specific task you shouldn't use a human body plan. Why design your kill bot like a person? Six legs or maybe tracks and low body plan with a 360 degree sensor suite would be more useful than looking sexy. If you are designing a sex bot then I really don't think it needs to be faster and stronger (and a deadly shot!) and in fact most 'users' would be more comfortable if it wasn't.
I think Star Wars is an excellent model. Another interesting, but very different, possibility for source material is the android in Dark Matter. Even though the crew often treat it as if it was a person in most ways (during season 1 at least) the android is very clearly a piece of property and it is completely aware and accepting of that. Of course it is a very valuable and useful piece of property which means nobody is ordering it to jump out a window unless there is a very, very good reason. Most RPG groups would not be happy to have a player that is faster, stronger and tougher than them without some significant drawbacks though.
Perhaps the best source of ideas would be the TV show Almost Human. The robots in this are very much hampered by their built in requirements to assist and obey humans. I'd be impressed with a player who managed to roleplay one of these effectively.