That first pic is commonly know in the States as Goat Head, it will grow anywhere and everywhere!!! You can never get rid of it, and the seeds have huge spikes on them. It's an incredible plant and I believe it's an ancient one too, don't quote me though...
It is Euphorbia on both images :)
I'm dumb, Goat Head has larger leaves...my bad, when you picking weeds they all start to look the same.
Haha they are all weeds after all :)