Spikey Mystery Plant

What is this? two of these appeared in containers in my front yard this year... I pulled one out of wine barrel #1, but the other I let grow just to see what it was.

At first I thought it was some kind of grass, but the leaves are serrated on the edges (very finely, and sharply!), but then this happened:

here's the one I pulled out of the wine barrel a few months ago...It was hard to remove and had a large taproot.

Mystery Plant...

One of my plant containers sprung a plant out of nowhere - seemingly overnight - that I don't remember ever purchasing.

It's possible it's some kind of weed, but it could also be something I bought that died back over the winter... It looks like a geranium.

If you know what it is let me know!

Las Vegas Mystery Plant

Who can tell me what this one is? I saw it growing all over Las Vegas, NV. I love it and I want one.