The only ones I have experience with are:
Halflings. Possibly the most powerful race in 5e because they are 5% better at almost everything thanks to Lucky. Any time a DM says "critical fumble" I say "halfling." Bountiful Luck extends the benefit to the rest of the party. All true luckmancer characters are halflings. The rest of the species ability suite isn't terrible either, unless you want to swing a Big Sword or grapple.
Goblins. I wrote and ran a "Goblin Defense" campaign (on the DM's Guild). 3 Goblin PCs + minions build and defend their lair against adventurers who are always higher-level than they are. They dug a lot of Small tunnels, firing ports for crossbows, etc. It was fun! The innate Cunning Action is very powerful.
You could say much the same about kobolds as goblins, except with some different species-specific abilities. I could sub them into Goblin Defense with no problem. I just haven't been interested in doing anything with them. Maybe if I do a dragon minion campaign... but kobolds feel like they should be silly rather than serious.
I think Gnomes are supposed to be the artificer/inventor/machinery types, and that's not my thing or a thing in my settings. Except they also talk to animals? Are they the Keebler Elves? I don't know.
Autognomes are...robot gnomes? Warforged already own the robot slot, and they are much cooler.