I swear I used to play this on Armor Games, but at least 3-4 years ago, and I can't find it anymore.
-Castle game, no scrolling, castle on the right-hand side with warriors on top, waves of enemies coming in from the left.
-Between rounds could sell items found, buy new weapons, recruit new warriors, etc.
-Different classes of warriors could handle different weapons. Set in a castle but had plenty of modern firearms.