[Admins]

I have heard of problems with the sword in earlier versions because the player was always in pause mode, but i have not seen any problems with the recent versions and was not able to get in an un-hurtable mode (tested with some people although it's not easy to find a server who still uses the old clientside-hurt detection). If you think you know some way to do that, please report it on the bugs forum.
There is no problem with the projectiles, the detection is on server-side.