Just joking. But if you should be able to know what weapons who's in the future, you'd need to travel in time. A time-traveler is not invented yet, so to get one you need to wait until it gets invented. Then you can use it to enter the future, but you don't need to, you are already in the future then.
As a weapon, I say a weapon my brain recently invented. But it's to hard to explain what it is.
Lightsaber. I'm more a fan of swords than I am a fan of guns. I like the Kung-Fu-leetness with all the spinning and flipping and airbornizationing and other epic ninja moves.
Lightsaber's just my style. Or a Katana with a blue or red aura that cuts through practically everything.
A field that you could put over the place you are protecting, that would distentegrate anything that tries to enter it. It can be shot and blown up(enlarged) then with a press of a button, gone. So it could be used for protection, but if you made it small then forced someone to go into it, it could be used for agressive tactics. (oh and all the matter that is distentegrated just turns into liquid.
