What's the most interesting or your favorite amino acid and why?

D-phenylalanine (enkephalinase inhibitor)

Interesting substance, its one of the few dextro (right-spinning optical isomer) amino acids that you can process or something.

I think its fascinating because its purportedly an endorphin reuptake enkephalinase inhibitor? or something so its potentially quasi-opioidergic. I'm not sold on the notion its legit but its definitely a provocative idea.