The one that comes with it? You just shake it up and down, and it'll flow. It works fairly well. My only complaint is the 10 minutes or so that it takes to drain the tank. Well that and where you put the now fuel smelly hose afterwards. I usually time it so that I'm doing this at a time when I'm going to stopped for a while so I can let the hose air dry. And if you're careful you can keep the gas smell off of you.
One guy did build a wired in pump setup that looked amazing. But I personally would be hesitant to put a hole in, in the bottom of the tank. You have any sort of failure there, and it's leaking all over the place.
If you are using a pump you can put the hole at the top.