May be a joke to some, but I find these low-cost dollar-store LED strings fun and useful. The lumen output is not all that important, they are mostly decorative. Some get use as nightlights, helping running down my boundless supply of free recovered alkalines. Sometimes cells leak but I just clean it up and carry on.
White is great but I also like colours. Recent trend is away from true colour LEDs, using white with coloured plastic overtop. Fortunately I bought up a good supply of single colour LED strings while more common: blue, red, orange, yellow, and green.
Some these contain a timer, using a small control IC and quartz crystal.
My beef with white strings using 2 cells (AA or AAA) is when total drops below around 2.5v, brightness will fall off leaving a fair bit of unused capacity in the cells. I disposed of these and kept ones using 3AA or 3AAA.
A neat $1.25`($1.50 Canada) light string from Dollar Tree uses 5-foot thin clear plastic tube with bubbles along the length and one LED at each end (2AA). Bubbles light up as small dots along the length, a form of passive lighting. Comes in orange, red, green, green and white. They are mostly seasonal product.
Dave