Sure, they make berries (something like a blackberry). If only that made up for their painful thorns and relentless invasion of every nook and cranny. With a good pair of gloves, you can pull them-- but you rarely get all of the roots, so they just come back later. To kill them with RoundUp, you have to be very persistent with repeated treatments.
Greenbriar / Saw Greenbriar
I hadn't noticed this in our yard until the past few years. Pulling/cutting it off at the ground won't do the trick. I dug one out from near our pink climbing/rambling rose and was stunned by how huge the root was. Heavy, too-- like some sort of devil potato. ;o) There are a couple growing up some crepe myrtles, and I dread dealing with them. When they come up right near the base of a tree, I can only imagine it's a challenge to get the whole tuber out without making a mess of your tree's roots. Oh, and they have mean thorns.
Sheep Sorrel / Field Sorrel
I actually think this weed is kind of pretty with its dangling little coin-shaped seeds (or whatever those dangly things are). It's not difficult to pull (though maybe pulling's not enough to eliminate it). However, it's unwanted, and there's a lot of it-- and I always have a hard time telling the difference between sheep sorrel and annual coreopsis, in early spring, which makes it difficult to know which plants to pull and which to leave.
Japanese Climbing Fern
We have a couple of slightly different-looking types of climbing fern in the woods around here. At least one of them is this horrible stuff. It's begun to invade the yard. Japanese honeysuckle is bad, but this stuff seems worse. It will smother plants-- even trees-- and though it has a pretty, delicate appearance, nothing could be further from the truth. It's amazingly strong and difficult to pull or break. I've read that you can kill it with RoundUp.
Gripeweed (a.k.a. Chamberbitter)
This one has several aliases, but I find "gripeweed" the most apt. I may be wrong, but I suspect the name originated with its reported medicinal use as a remedy for digestive troubles, but trust me, if this weed ever gets established in your garden, you will do plenty of "griping" about it. You'll have endless opportunities to gripe as the thousands (millions? billions?) of seeds it drops germinate in the warm weather (in wave after infuriating wave). You'll swear that you could spend every spare minute of the summer pulling them and still miss a few. You'll gripe some more when you see how quickly they shoot up-- and threaten to scatter still more seed before you can find and pull them all. (The seed pods explode to throw the seed as far as possible. Each one is literally a weed-seed-spreading BOMB. Or maybe not. Anyway, you get the point; it's horrifyingly awful, from a gardener's perspective.)
Each little plant is not that difficult to pull. The problem is that (once established), there are so many of them popping up EV-er-y-where. And once they start setting seed (which doesn't take long, let me assure you), you have to be very careful not to spread the new batch of seed around as you weed.
This truly is a vile weed, and yet-- apparently-- Phyllanthus urinaria has many uses in the world of herbal medicine and can even be expensive. (I find that difficult to believe, however. The stuff is so prolific; how could it ever be rare enough to be costly? ...Unless it has to be extensively processed... Anyone who wants to make a quick buck, hurry over with empty buckets. You're welcome to all you can pull.)
I didn't know what this one was called until I recently bothered to research it. This is only my best guess, but the descriptions fit it to a T-- and it certainly looks the same.
Imagine, if you will, a grassy weed so fiendish that it has earned common names "creeping panic" and "panic rampant". Oh, okay, so that's probably based on the Latin name, Panicum repens. To me, it still evokes the vivid mental image of a hapless farmer or gardener running around in a, well, panic after discovering a fresh infestation.
The name "torpedograss" was given it because of the sharp tip of the weed's rhizome, which pushes through the soil and is rumored to be capable of piercing landscape fabric, weed barriers, and Kevlar. Long before I knew what torpedograss was, I was cursing it as I pulled, pulled, pulled and dug, dug, dug. Pulling is practically useless. It will continue to come up. Probably not indefinitely, but most likely you'll give up before it does. Digging it is better, but still no guarantee of eradication, because the rhizomes grow in such a crazy way-- horizontally, up to a foot or more deep.
Many times, I've dug/pulled up layer after layer of the darn rhizomes. "That must be all... It couldn't go any deeper than that. ...Wait. No. No, it-- it can't be... another level?! When will it ever end?! It's a conspiracy! A conspiracy, I tell ya!" And of course, if you miss a piece, it just shrugs its metaphorical shoulders and sends up some new shoots of grass.
You can kill it with RoundUp, they say, but when it's in amongst your good plants, that's not a fun job.
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That's just scratching the surface of my personal "collection" of weeds-- let's not forget chickweed and henbit and spiderwort and dandelions and thistle and spurge and nutgrass and geranium weed and that weird one whose name I don't know, with the little football-shaped seeds/pods covered in Nature's version of velcro-- but it's most of the worst offenders (to date).