The two most valuable rental codes I have ever come across are both from National. One includes LDW, but I hesitate to use that because if something does happen, that would trump my AMEX primary insurance and since this code is intended for a certain group of employees, there is the potential of no coverage or a messy battle that I do not wish to deal with to save $19.95. In any case, if that is not a concern for you, that code is 5000062. Generally, the code will give you a cost of $32/day including one way rentals. A similar code without LDW which has sometimes lower sometimes higher rates ($30-40/day) is XZ38140. It too is good for one way rentals. Both codes are also useful for high cost rentals that are not one way.