Considering all weapons available to all branches, which weapon have you been in awe of? Why?

The B-52 BUFF. Ugly, mean, old, and dirty. Gravity nukes, ALCMs, and SRAMs. Harpoons, mines, and electronic warfare. Low altitude, high altitude, worldwide recognized ass kicker. Listening to eighty one (81) 500-pound bombs pound man-made thunder in your direction has scared the living crap out of every person who has had the misfortune to be nearby. For nearly a full minute, a 500 pound bomb is exploding every half-second, and there's not a damn thing you can do about it.

The individual soldier on the ground, committed to mission, highly trained, with a sharp knife and tactical support.

M-60 machine gun. It was reliable, great distance, changeable barrels, and very dependable.
I also liked the M-14, which was dependable, and hit like a train whatever it was aimed at.
The only advantage the M-16 toy gun offered, was less weight. It failed in all other areas.