Which of the following is not ordinarily used as a rodenticide?

Methoxychlor is primarily known as an insecticide and is not typically classified or used as a rodenticide. Its mode of action targets insects, particularly as a replacement for DDT, and it disrupts the reproductive and endocrine systems in these organisms. This differentiates it from the substances commonly used to control rodent populations.

In contrast, ANTU, sodium fluoracetate, and warfarin are all compounds recognized for their effectiveness as rodenticides. ANTU is a toxic compound that works by causing respiratory failure in rodents, while sodium fluoracetate affects the metabolism in mammals and is lethal in small doses. Warfarin, commonly used in veterinary and human medicine as an anticoagulant, works as a rodenticide by preventing blood clotting, ultimately leading to the death of the rodent due to internal bleeding.

Thus, while the other choices are traditionally utilized for rodent control, methoxychlor is not employed for this purpose, making it the correct answer.