I've never wielded the Dragonslayer (legitimately anyway, it's part of the IDKFA cheat but eh). I've probably seen it twice, ever, in any game at all. Even knowing what it does and how to get it, my reaction was summarized by an "okay cool" and not much else. Like a lot of stuff in the game, it can make things WAY too easy, which isn't the kind of fun I have with this game anyway.
Whenever people ask me how to get it, I just tell them to figure out what inspired it: this is more than enough to bring the conditions to a small set of possibilities, all of which can be feasibly attained and/or employed in the course of a single game. I don't really care whether or not it's a secret, but I also don't want to betray Kornel's trust by leaking it. Ultimately it's his decision.
First thing I'll do when the DoomRL source/core game modding tools come out is remove the horrible, horrible injoke.
As is totally expected, then, the current modding tools (0.9.9.4) allow you to spawn any item you want...except the Dragonslayer and Berserker Armor.