My almost-13-year-old asked most seriously to be someone named "Agent Washington." I didn't have clue who he was, but I was quickly educated about Red Vs. Blue and Halo and immediately terrified of creating such a complex costume.
In desperation for ideas, I started trolling the thrift store. I scored there and found martial arts sparring gear for $10. After a failed attempt at dying the set, I pulled out all the pads, sawed, cut and otherwise shaped the pads and helmet, used a ton of hot melt glue and upholstery foam as well as craft foam, a couple of plastic guns, lots of spray paint and a yellow Avery divider for the visor. Two weeks of work later...Agent Washington!