Snickersnee is also a lawful artifact weapon in NetHack. It's a katana, which is already a good weapon, and it deals an extra 1d8 damage to everything. It doesn't get any special bonus to hit, unlike Excalibur (except for the +1 that all katanas get), but this isn't really a serious handicap after XP level 5 or so. In terms of raw damage, it's equivalent to Excalibur against small monsters and only slightly worse against large ones. It's also not intelligent, so neutral and chaotic characters can wield it (although they'll get blasted). Further, it's possible for non-lawful characters to get without wishing. It's even the first sacrifice gift for Samurai.
While some players decry it for its relatively mediocre damage bonus, the fact that it's a strong base item, and deals bonus damage to everything means that it's generally a worthwhile weapon all the way through the ascension run. In particular, if you have Snickersnee and can get at least basic skill in longswords, it's probably not worth the effort to wish for another artifact weapon. (Except maybe Magicbane, and even then only for its engraving and magic resistance properties.)