There are also drive by ones where you can get infected simply by going to the website
These are the kinds that you really need to worry about. It's the main reason why I always run ad blockers, because I haven't seen a single advertising site that actually cares enough to filter out any potentially malicious adverts, including Google.
The drive-bys exploit flaws in your browser in order to automatically infect your computer without downloading any executable file. It's really bad.