HabitRPG
Used by 2 peoplehabitica.com ↗

“My main productivity and organizational tool is Habitica, also called HabitRPG, a gamified online productivity program.”
Ada Palmer Interview, Science fiction & fantasy novelist, history professor, musician · via Uses This 
“I've also been using HabitRPG as a fun to-do list manager and habit builder.”
Ryn Daniels Interview, Web operations engineer (Etsy) · via Uses This