Kids for me. On my third one. It is hard at times and you sacrifice a lot of your time, and energy (money is less of an issue up to the second one I'd say, the real costs starts at three where you need to upgrade cars and shit) in order to be a good parent. But watching them grow up and be brilliant boys, is very rewarding. I am happy that I am providing them a good life so far, they are smart and devour knowledge, and they take on my interests kinda naturally so it's fun teaching them things I enjoy.
In a few years we will be nerding out on Dota or PoE or whatever, anime, maybe I will DM an rpg for them and their cousins that live nearby. Start them up with python or so. Teach them Japanese, maybe have them start tennis or so. Or maybe they will nerd out with something on their own. Well see..
Tomorrow I'll grab the boys and go to the countryside for hiking up the mountains, playing in the forest, eating awesome food in taverns and so on. Will be tiring, but will be fun.
So yeah. Kids are fun and they give me a purpose to strive for. Peace and quiet while being alone was definitely something, but after experiencing both, for me it is purposeless, unfulfilling, and gets pretty boring pretty quick.