One of the few persistent complaints I've seen regarding ACKS is that we may Spears slightly *too* awesome: Useable with one or two hands, throwable, able to attack from the second rank, able to set for charge, their only downside is that they are encumbering and easier to sunder. While I can make arguments for the reality that the spear was the ultimate weapon of ancient warfare for thousands of years, it still might be too much for your campaign. Therefore I offer the following houserule:
Spears May Be Shattered
When attacking with a spear, an attack throw of natural 1 results in a nomagical spear's haft being broken. A magical spear's haft is damaged. A magical spear can be damaged a number of times equal to its bonus before its haft is broken. A spear with a broken haft can be used as a dagger or a quarterstaff, but no longer functions as a spear.
A nonmagical or magical spear can be repaired by setting the spearhead onto a new shaft, which costs 1gp and requires 1 rank of Craft (weaponsmithing).