Yeah, you may be on to something with the minibamboo. These seem to grow about 1-1/2 foot high if left unattended. They seemed to have started from a downspout from a neighbor's yard, but spread quickly. Hmmm, there must be some other method of removal other than pulling or Roundup.
The first plant I identified above is still cropping out at different points in my lawn. A spring application of Scotts Halts Plus caused these to start turning yellow as summer progressed, but it does not kill off the plant. Barring a chemical application, I will see if hand pulling eradicates it. As you can see from the picture, it has a small, four-pointed flower, which turns into a "nut" of sorts in late summer. It can form dense mats, making me think it's another highly invasive ground-cover that has escaped from someone's garden. I would still be quite interested in knowing what it is and what might chemically eradicate it.
I was able to finally defeat the "Frankenbush" that was in the corner of my yard. That bush sent out LONG runners - as long as 20 feet. The bush was well established when we bought the house. Digging it out with a pick mattock revealed runner roots that were white in color. These broke easily when dug out, and each root section created new plant sprouts. It was only after I had dug up all the soil a foot deep around the bush that I could locate every stem section and remove it from the soil. For three years after, new plants continued to sprout around the bush, and careful digging with the pick mattock revealed the root section, which were removed. I think I've just about ridded the yard of this nightmare bush, whatever it was. Now on to the Rose of Sharon Hibiscus, another bush I should have never planted in the yard. Those were dug up and sent to the dump. The sprouts are showing up all over the yard at this point. Maybe in three of four years I'll have all those pulled.