The coolest thing in HOI IV...

...is equipment, and especially naming it. Seriously. The ability to create any combination of modules for tanks, ships, planes, producing custom named EQ and ability to ship it to other nations, sell it or sell the patents, capturing equipment and coming up with designations for them, noticing stuff you created somewhere on the battlefield is just so good. I literally had games where I'd just stay put, stamp out EQ and ship it. What's the coolest thing for y'all?