A figurine of an Archon. It has Sunsword. Now you have 2 options: the moral one, or the immoral one.
The moral one: enchant its sunsword to +6 or +7
The immoral one: Take its sunsword for yourself and ascend without wishing for any artifacts (quite a good conduct)
I chose the moral one, but remember, archons are always generated with either demonbane or sunsword (demonbane first, since they are angels)
Sunsword blinding the monster + archon blinding the monster + sunsword and archon's massive damage = A dead monster :D
This is also a good wish for a player wanting the pacifist conduct, since the archon kills pretty much everything you need to kill to ascend.
Or just wish for an artifact, like Stormbringer. Even if you are of another alignment, the worst it can do is blast you (but make sure it isn't intelligent, like the longbow of diana, because it is a wish wasted: "The Longbow of Diana evades your grasp!"). Stormbringer provides level drain resistance and level draining. I always wish for it, even though almost every character I play is neutral, and Stormbringer is chaotic.