I don’t know if you would call Hobbits Halflings monster races but they are my favorite. I love the way Eberron did them with their mark of hospitability so they have special magic to make everywhere more comfortable and good things just happen to them. I love how they just took the fearlessness and everything good from Kinder and just wrapped it into regular hobbits halfings.
I love Goblins as well so I always make mine Pathfinder inspired so they will be green with a big head who love fire and general chaos instead of orange like dnd goblins. They are always fun since they like to straddle the lines between disgusting, cute, destructive and helpless. I know my players always will befriend them so I like to put a lot of them in there.
I also like to treat them like cockroaches or fruit flies who breed very fast and can adopt to any conditions. So there will be strange variations based on where they live. Mud goblins, fire goblins, moss goblins who just have small physical adaptations to better fit their habitat.