I'm going to start a series covering my take on common weapons and tools used in dungeoneering. First up: the spear.
It's a common misconception that the spear is a perfect dungeoneering weapon, and I think this misconception comes from the idea that all you do with a spear is poke people with the pointy end. While that's certainly a key point of the art of spearfighting, it's far from the whole picture.
I should point out here that I'm not talking about soldiers in a phalanx
(which most RPG's don't deal with), but rather about single/small group
I recently bought two 8' hardwood shafts to use for spear drills. My first reaction on bringing them into my house? "Crap, these are big!" Historical spears ranged from about 6' to maybe 9', so my spears are on the long side, but my conclusions hold more or less for 6' spears.
There is almost no way I could effectively fight with a spear indoors. Navigating through hallways is a pain. Doorways are a bigger pain. Corners are a pain. Turning the spear around is impossible without whacking into walls and bumping off furniture.
Much of spear-fighting consists of off-line guards - holding the spear vertically, or pointing it straight backwards. These off-line guards allow a strong parry with a turn of the hips, knocking aside your opponents weapon and leaving them open to a thrust to the face.
If your spear is parried, you can take the energy of the parry, and swing the back end of the spear around. This counter-parries, and allows you to strike with the butt.
These turning motions are *critical* to spear combat.
Trying to do them in an enclosed space with other warriors around you would be difficult at best, and impossible at worst. My experience fumbling around with an 8' pole in my house has convinced me of that.
Trying to fight without them would be lead to a marked reduction in spear effectiveness - something on the order of halving your combat effectiveness, I would say.
For D&D - halve your AC, and miss on any to-hit roll of 10 or less when spearfighting in an enclosed space.
For S&S - no Attack or Defense bonus from your spear, miss on any to-hit roll of 10 or less.