Many have commented on how in RPG's like D&D the shield seems to not account for much on the defence. Yet in the real world the shield was the earliest and most effective form of protection. It was part of the fighting man's arsenal from prehistoric times until when improvements in armour and firearms led to their decline. The sheild carries on even today in the hands of riot police. Anyone who has done SCA heavy fighting can tell you, its hard to get past a sheild. In D&D all sheild types and sizes are lumped into a single small bonus of 1 to your armour class. In an earlier post suggested alternative bonuses for size. But in the shower today (imagine that, a gamer who showers every day) I had a better idea. What if your AC was based on your shield type and armour worn was a bonus. The size and construction of your shield is taken into account ie a large wicker shield would not be as good as a small metal one. Armour would account for a smaller bouns to your AC based on type scalling up from simple cloth or padded all the way up to full plate. Full knightly plate could provide a large enough bonus that carring a sheild is now redundant (something that happened historically)
I will post some examples later.