I have an idea for one. This particular enemy can be any other type as well (usually combining with a type that makes them harder to kill) but uses one particular trick. It's attacks deal no damage up front and its immortal until it reaches 1hp. Instead, its attacks add a state that "stores" damage (and the player cannot see how much). It also tends to be a high agi enemy with more than one attack (or action) per turn.
When the enemy reaches 1 hp, it deals randomly between 50% and 200% of the damage it has stored in the player's states before it dies.
Well.. I was going to post my randomly generated road experiments... But the new "Attach Files" on profile posts seems to be quite buggy. Also there's no more option to insert Imgur images. Highly unfortunate. Guess I'll give them a bit to fix it and go back to messing with stuff.