Halfling Swashbucklers are boss. Ratfolk aren't bad either with inspired blade. Mouser builds can be crazy.
Gnomes make pretty good sorcerers and oracles.
Any small sized race can pull off a mounted build that can go anywhere, halfling and gnome cavaliers can be pretty epic, you're really just losing ~2 damage and gaining lots of swagger.
You can play small sized Aasimar, Skinwalkers and Tieflings.
Grippli bad touch cleric killing with his tongue, free net proficiency for shenanigans in combat.
Kobolds for hard mode. Love me some Dragon Disciples though... Especially the Flame Oracle ones. Yeah.
A Rogue3-4/Fighter x Halfling Dagger specialist with Startoss Style Feats and Dex to Damage, Risky Striker, Piranha Strike and whatnot might be groovy.
Halfling Master of Many Styles 2ish/Underground Chemist x with Slipslinger and Startoss Style feats.
Halfling Urban Barbarian 6/ Shadowdancer 10 Use Spirit Totem to heal your Shadow. Halfings make great Urban Bloodragers too.
Gnomes make great illusionists and Kineticists. Halfings do good with psychic magic due to their save bonus against fear, go with one of the charisma casters for all of these.
Small characters have a lot of options. This doesn't even scratch the surface.