Sri Lanka's flag dates back to when the Mughal Empire ruled India, very cool.
Also, not really a country flag but cool all the same. The Austrian Grenadier Battalion Purcell Regiment had a good flag.
You can buy black powder ammunition and operate a flintlock or percussion cap weapon as young as 16. You also don't need a permit as well. (Mainly for reenacting of course)
Congrats on turning 18!