Hmm, I didn't want to say anything yet, but here's a halberd/axe I just put together. It's a weapon from the AD&D module The Fall of Myth Drannor. All stats are authentic!

Heartcleaver: Vorpal Axe +3

This monstrous executioner's axe is balanced and sized for large humanoids; humans and the like must wield it two-handed as a halberd. It requires 18 strength to use. The axe blade is as massive as a medium shield, with its razor-sharp edge constantly dripping with a poisonous green ichor. This weapon is not native to the Realms, but was forged on Gehenna.

Heartcleaver was the weapon of the monstrous nycaloth Gaulguth, the warrior of the three nycaloths at the head of the Army of Darkness that sacked Myth Drannor in the Year of Doom. After Gaulguth's death at the Battle of the Lost Trench, the axe was reportedly lost among the baatezu-infested ruins of the former City of Song.



STATISTICS:
Special ability:
25% chance to instantly kill opponent (save vs. death/poison at -2)
+2 points of poison damage per round for 6 rounds (save vs. death/poison for none)
THAC0: +3 bonus
Damage: 1D10 +3
Damage type: slashing
Weight: 20
Speed Factor: 8
Proficiency Type: Halberd
Type: 2-handed
Requires: 18 Strength
Not Usable By:
Druid
Cleric
Mage
Thief

What do you guys think? I also fixed the colors up to make the axe blade glow luminiscent green.