Lego's Refusal to Make War Toys
Other Compatible Brands Fill in
Lego wants to be seen as a family friendly toy. They do not want to be shown as supportive of modern violence. While weapons are included in sets like Castle, Star Wars, and Ninjago, they are not the sole purpose of the set. With this "gap" as some see it in Lego products, many other brands fill in.
I'm not sure if they compete with Lego war-toy wise, but the Lego company doesn't like them
This Canadian based company is known for its sets from TMNT, Halo, Minions, Assassin's Creed, and most famously, Call of Duty. These characters are more realistic and posable, with 12 points of articulation as opposed to a Lego's 7. The weapons are customizable and more recognizable. This is most retailed of all the "War Brands".
Call of Duty Collector Construction Sets
Kre-O is a Lego-like offshoot of Hasbro. They make branded sets like Transformers.
KRE-O TRANSFORMERS BEAST HUNTERS AUTOBOT COMMAND CENTER TV COMMERCIAL
Cobi is a Polish toy company, but is quality is closer to cheap Chinese crap. Trust me. I found out the hard way.
Small Army WW2 (30s) Top Secret - cobi.pl
Alright, it isn't a real company, but it offers some pretty sweet guns.