If breastfeeding, nothing, you've got it covered.
Otherwise, cow's milk or formula would be best. Goat's milk second best.
After that, toss up between soy and hemp milk (both fortified, full fat versions).
Almond milk or hazelnut after that, maybe. I wouldn't be comfortable with it.
Rice milk, no. Too little fat, too little protein. Google it, there are serious risks of protein deficiency.
DS is allergic to cow's milk and gets a combination of formula (Neocate), breastmilk (very low supply), hemp milk, almond milk, hazelnut milk, and soy milk.
It's an ongoing worry for us, whether he is getting sufficient nutrients. If there were no breastmilk supply problems, he'd get that. If there were no allergy issues, cow's milk or even goat's. If his formula weren't so darned expensive ($50/can), he'd still be on that all the time.