Nothing too profound here. This is just a thought that's been bouncing around my head the last couple of days.
The Flail is too powerful. It can turn a Strength 1 Sprite into an unstoppable force. I'm not a big fan of there being single objects/followers/etc. that can throw the game that far out of balance so easily--especially since you can get it for 1g or less (under the right circumstances, of course).
If it were up to me (which, outside of my own house, it isn't) I'd change the Flail like this:
1) You automatically roll a 6 for your attack roll in battle.
2) Roll two dice. If you roll doubles your opponent may not roll for his attack roll.
It's still powerful, but no overly so; and it still gives the chance for your opponent not rolling. But it also make the Great Sword a more favorable option. Do you want a +3 with an die roll added on top? Or do you simply want an automatic 6 for your die roll? Just so long as you have a higher strength than your opponent the automatic 6 is an automatic win. But you can do better than that half the time (statistically speaking) if you take the Great Sword.
This seems to balance out the Flail, bringing it down to the level of some of the other weapons in the game.