Excalibur

Excalibur is a very easy weapon to get (if you are lawful). Simply dip a long sword into a fountain, provided you are a lawful character and level 5 at least, and level 7 for preference. It's intelligent, so it can only be safely wielded by lawful characters. As a weapon, it does +d5 to hit and +d10 damage. What's equally useful is that it confers level-drain resistance and automatic searching, and makes searching more likely to be successful. OTOH, it also makes demon princes guaranteed hostile, and every monster can find you, O Paragon of Virtue.