I'm using The Boss 7 ton splitter, I bought it at Home Depot. I'm very pleased with this little machine.
This is chestnut oak, great firewood, it has as many BTUs as white oak. This stuff is rather stringy and difficult to split. On the big pieces, I make a little chainsaw cut, 2 inches deep, and then the splitter cuts them right in half.
The woodshed is just about full. The dark wood, the top 2/3 of the stack, is what I put in today. Below that is ash, left over from last year, and a little black walnut in the corner.
I like ash and black walnut, but chestnut oak is much better, I don't mind that it is hard to split.