If you can get the heart from a recently slain Frost Giant...for 100x the normal weapon cost§, a witch can make you a weapon that has the following features. They manifest based upon your experience as an adventurer, mastery of yourself, and the emotional resonances the weapon will pick up from you while adventuring. The weapon or item can be created to respond to cold/ice/frost based creatures OR heat/fire based creatures, but not both. 100x the weapon cost in coins/gems must be destroyed at each level denoted to reinvigorate the magic, otherwise it will stay at the lower level of ability.
Wielder's Level / Ability
1 / Will shed light as a torch within 30 ft of and point to like a compass needle if let go; 1 round of no proximity damage
3 / plus 1 bonus to hit and damage VS creatures of this type; wielder gets +1 bonus to saves VS
5 / plus 1 hit/damage in general and +3 to hit, damage, and saves VS creatures of specified element; protects wearer as Ring of Reststance to appropriate element
Items that launch missiles can be enchanted and thus all missiles launched by it have the effect.
§hence, if a mundane example of the weapon can be bought for 15 GP, one must spend 1500 GP to make one of these.
The following weapon can be crafted for 10x the cost of a 2 Handed sword:
Stupidly Huge Anime Sword - a 2 handed sword that also counts as a basic shield. No additional shields or weapons can be wielded without spending a round dropping this sword and getting them. This sword can only be wielded by character with a 14 Strength or greater unless it is enchanted.
EDIT a few hours later: fixed formatting and increased costs to what they should have been.