Not to be a negative Nancy, but many of the mods here are not really needed. There are some quality ones that tweak behaviors a bit, but unless you know what you are looking for it's a free for all.
I also don't want to list which ones are fast, because it's irrelevant for many - a better test is comparing hacks that do similar tasks. I also can't recommend any because it depends on your needs.
If you can post more info on what you are actually looking for then I (and others) can be of more assistance.