Zbblock is effective and pretty strict. It kills most spammmer, hackers and scrapers in their tracks and saves me about 40% of my monthly bandwidth. I was also able to drop the resources on my cloud server and saved money.
Oh and drop in a "bot trap" as well. Create a robots TXT and forbid spiders going into a directory /bot/ for example and then just log the ips of all users that hit this directory and ban them. I have these auto added to a deny from in .htaccess and legitimate users can even remove themselves.