Played a game several years back (AD&D 2ed, that far back) where the DM did have breakable weapons. He made up a rather simple system that allowed for weapon breakage that was easy to keep track of for him and for us, and it did add a good point of realism. You don't have to use these, but this was the basic house rules set that we used, broken down by materials.
Each successful strike with (or against) was a point, and each item, based on its material, had a number of points. Leather armor would eventually get shredded after so many cuts and stabbings, and shields did break, especially with blunt weapons.
Wooden weapons (Considered useless at 0, considered broken/shattered)
Bows, Staffs, Cudgles, Clubs, Staves, and polearm shafts.
- Teak - 25 points
- Pine - 40
- Walnut - 65
- Chestnut - 85
- Oak - 100
- Hickory - 110
- Redwood - 150
Note: Arrows were considered single use, as shafts/points/fletching would be ruined in battle)
Metal weapons (Considered clubs/maces at 0, considered dull. Knives were considered chipped and dealt only subdual damage.)
- Copper - 15 points
- Bronze - 35
- Iron - 45
- Steel - 75
Wooden shields (Considered useless at 0, considered shattered)
- Plain wood - 10 points
- Wood with hide - 15
- Wood with copper - 18
- Wood with bronze - 22
- Wood with iron - 30
- Wood with steel - 45
Metal shields (Half effectiveness at 0, considered misshapen)
- Copper - 15 points
- Bronze - 20
- Iron - 30
- Steel - 50
Leather Armor (Useless at 0, considered rags)
- Cloth (padded) - 3 points
- Hide - 5
- Scale - 7
- Bone - 8
- Leather - 9
- Boiled Leather - 11
- Studded leather - 14
Metal Armor (Half effectiveness at 0, considered bent)
- Copper - 10 points
- Bronze - 25 points
- Iron - 60 points
- Steel - 85 points
This wasn't the whole list of either weapons, armor, shields, or materials available (not to mention improvements and maintenance). Having some points in smithing, fletching, bow making, and leatherworking became rather critical, as you could only improve base upon the modifier + time worked upon each piece of equipment.
This is only what I remember, but the whole thing was a lot more comprehensive. There were more than a few situations where we had weapons that weren't effective, and armor that was only practical as clothing. The baddies, too, only had a certain amount of points on their stuff based on their CR (I think it was X1.25 their CR) and feats like sunder, disarm, cleave, and batter (which we invented) became extremely useful. Improvised weapons and pick-ups were the way of life. I think at one point of time one of our PC's was using someone's Iron Chest Plate as a shield, as it lasted twice as long... and he couldn't get anything else in a cave.