A creeping perennial grass that invades lawns and stands out when it turns brown while your turf stays green.

It forms a dense, low mat with thin, bluish-green leaves. It spreads by stolons that root at each node, similar to bermudagrass, but you can tell them apart by looking at the small membrane-like structure where the leaf meets the stem—nimblewill's is smooth and papery, while bermuda's is hairy.
Often mistaken for: Bermudagrass (check the ligule to tell them apart)
It's a perennial, so it's around all year, but it's easiest to spot in late summer and fall when it browns out ahead of the rest of your lawn.
It shows up in home lawns of all grass types, spreading as a creeping mat.

A sneaky summer weed that looks like grass until it flowers, showing up after most pre-emergents wear off.

A low, mat-forming summer weed that moves fast into thin or bare spots in the lawn.

A coarse, clumping perennial grass weed that stands out from your turf and spreads by seed if left alone.

A summer weed that thrives in soggy lawns but, unlike its cousins, doesn't come back from roots year after year.