Warfarin is mostly obsolete in terms of rodenticides. It's classified as a "Gen 1 Anticoagulant", which took many feedings to work, and most rats are now resistant to Gen 1.

There are a number of other rodenticide classes, like cholecalciferol (calcifies the blood) or the broader "Gen 2 Anticoagulants", like "bromadialone".

Bromadialone has the benefit of being much less likely to cause harm outside of the target pest, due to needing much smaller amounts to affect the rodents.

Bromadialone also has the added feature of being reversible, with an acute dose of vitamin K.

God that sounds on par in fuckedupness as arsenic.