Promethean wire.

Seen it in the trailer was wondering if Spartans could also harness the unique tool? Imagine throwing a grenade back at an enemies face?

You mean the thing that Watchers use to hurl your own grenades back at you?

People would complain about adding that feature and we would never hear the end of it besides isn’t it impossible(excluding watchers) to throw back a primed sticky grenade?

yes. could use it to hurl grenades just like they do or it could be used for trip wire or to pull oponents closer to you. Either way its all good as long as we can use all of it. OR used as a rappeling cable!!!