new weapons
The first step in creating a new weapon is to figure out what you want to name the weapon. It has to be a weapon name that doesn't already exist. So open weapons.db with Notepad and do a quick search for the name of the weapon you've picked out. If it doesn't exist, keep going. If not, come up with a new name.
Second step is to add the weapon to the correct list. In weapons.db you should see several lines at the top of the file. They're split by weapon types and then the monster/npc section. If you're creating a weapon for players to purchase, add it to the correct weapon type. If you're making one for npcs or monsters, add it to the last MonsterWpns line (currently MonsterWpns7). Either way, find the correct line, add a period followed by the name of the weapon (for example .TestWeapon)
Now you're ready to add the actual weapon.
Scroll to the very bottom of the database file.
You can find an empty template and an explanation of each of the various settings inside of the weapon here:
Weapon Template and Flags
For the sake of a tutorial, let's create a weapon for a monster called MonsterWeapon:
[MonsterWeapon]
Cost=0
Type=HandToHand
Info=A monster's weapon, players can't buy it.
Abilities=MonsterTech1.MonsterTech2
Element=fire
Hits=$rand(1,2)
Basepower=10
Upgrade=0
IgnoreDefense=0
HurtEthereal=false
Energy=0
CanShieldReflect=false
CanCounter=true
And there you go. You've now successfully added a new weapon.