Cornfield ants
"In addition to being harmless to humans – they don’t sting or bite – these ants are actually good for your lawn! They eat the eggs of grass pests, including Japanese beetles. One study found that when these ants were present in turf grass, they reduced the numbers of white grubs and other grass pest larvae. "
UPDATE in 2023: Just have to say, these ants always crack me up. They run around so quickly, like there is some emergency. Try sticking your index finger on/next to the entry hole and they will freak out super bad and run up your hand... attempt to bite you (practically tickles). Waaaay cooler than fireants, hope these dudes stay around forever.
