Time for me to finally submit something that ISN'T from Rise of the Triad. Be warned, though, this still needs some fleshing out to be both true to the source AND workable in DoomRL (yes I care that it's both).
Sword of Omens
Unique Melee
7d6 fire (unmoddable)
Alt-fire: Sight Beyond Sight: Increases dodge chance by 30% and allows dodging to work regardless of movement circumstances (as in, you can dodge even if moving parallel to the line of fire). Lasts for 10s and tires the user out afterward.
Special: Increases armor by 2 while either equipped or prepared.
Notes: The reason Pickup and Inventory quotes aren't yet supplied is because in both cases, I want to quote the series that is the origin of the weapon (in case you don't know, this thing's from ThunderCats) without being too blatant, and/or possibly break the fourth wall by wondering what this thing is doing around all these hellspawn. Since I didn't already have quotes prepared, I chose not to supply any of my own just yet, rather than submit a crap one and ruin an idea.
My excuse for the free armor is, well, the sword's sheath is actually an arm shield (claw shield if you want to be REALLY technical). Maybe this would work better if it was ONLY while the weapon was prepared, and not actually the equipped weapon?
Also, why does this thing do fire damage when it's very much a physical blade, you may ask? Simple. I note in at least the 2011 version of ThunderCats that the sword is capable of cutting through stone very easily. And yet, I don't want this doing plasma damage as then it's too much of a kid brother to the weapons in Unholy Cathedral. Giving it fire damage (which can destroy walls) is my compromise in this regard. (If you're familiar with this weapon in its sources and plasma damage is actually more justified, please let me know.)
Lastly, I'm working on trying to find evidence of this sword reflecting magic attacks in its own series (either the original or the 2011 version), as that's what I REALLY want with the alt-fire - reflecting enemy projectiles. If I can't find that, what you see here is one alternative. The other is a blast of energy (I want to avoid this if I can because it'll be too much like the Cathedral weapons again).
All in all, what I'm trying to develop here in terms of game stats is a weapon that won't entirely replace the Cathedral weapons, but may be worth keeping around even if you have them.