Figured this should be a good first post, aside from some applications.
Some other MUDs with the DIKU codebase have a stop command, one that lets you delete all queued commands. This is very useful for anyone who types north one time too many and doesn't want to step off a cliff.
Now, I tried using stop, and noticed it was a command made for casters, so I propose that a command like thisbe implemented under the name halt. Nothing fancy, just a way to cease all commands and come to a standstill.
I also realise that I'm new, and probably not the first to suggest this to boot, but I still think it's a good idea.