Dawnclucks22
Crowing
There are also mosaics, which are chimeras, except that the different-gened portions are scattered around instead of being a neat split. Neater chimeras aren't always half-and-half, either, it can be one limb, a few organs, or something like that.
There was a case awhile ago where an unfortunate lady nearly lost her kids because genetic testing revealed they weren't biologically hers. It turns out that her reproductive system has separate genes from the rest of her, she evidently absorbed a twin in the womb. That's how most chimeras are thought to happen.