For example, pomegranates:
My personal favourite is this mango tree. There's lots of stuff on the internet about how to germinate a mango, but this one grew really easily. Just break the hard shell, put it in dirt, and keep it warm until the magic begins. Here it is on day 2:
And here on day ... well ... 10 or so maybe (the green things around it are baby lemon trees):
It's that easy. Instead of throwing away the pit on your next fruit, try planting it! Such a simple way to get cute house plants.