One particular one I thought of would be to intercept any inputs beginning with /foo when foo is not understood. Thus /msg and /ignore would work, but /msh would come back to the input line along with a msg from root "/msh not understood".
This was inpired after seeing a serious of such typos...some intential, some not. (Those trying for the funny "typos" could still figure a way around it. \msg or .msg or whatever, the idea is to prevent mistakes that could prove highly embarassing.)