Anything that gives something useful for 'free' will bring a lot of traffic :-p. Entertainment related sites movies / wallpapers etc. get a lot of traffic but don't give that much revenue.
The above guy has it right... there is no such thing as a website that generates its own traffic right out of the gate. You have to bring traffic to it. Internet Marketing isn't a "build it and they will come" type business.
Yes any topic can get the good traffice.. You only need to Spend money/time to get it.. Either use ppc or Spend your time on content creation or promote your site yourself..
Take a look at the kind of sites that do well on social bookmarking websites. Certain topics can create more of a 'buzz' and get spread by word of mouth quite quickly. It's a matter of appealing to many people's interests. There are various link baiting techniques that can create even more of a buzz. As other people have mentioned, it just comes down to having a high quality site with high quality content.
how you guys can forget the social bookmarking for getting traffice?... btw stumblupol helps a lot. also try to find out good blogs and do proper and interesting comments on various posts... sure you will get good traffic from there.
i agree with vansterdam - if you have quality content that could do really well on social bookmarking sites you will get a lot of traffic fast. Visitors from social bookmarking sites won't click too often your ads but they will subscribe to your feed and will return to your site to see if you added something interesting.