Quicksilver?

It has more functionality than spotlight i.e it can edit files and rename files from the menu.

 

I always found Spotlight to be cumbersome for launching applications, so I have Quicksilver's preferences set to just catalog apps.

 

I really recommend you do a tutorial or two on QS which you can find on the Blacktree home page. The tutorials will open your eyes to the differences between Spotlight and QS and it is much easier to follow than any advice I (or anyone else) can provide here.

I find QS to be invaluable.

 

I hear you, but I do use Quicksilver regularly now.

I had heard it was one of the best things around, so I downloaded it and tried it three times and gave up, not seeing the point. But on the fourth try, I just focused on using it as an application launcher, and I began to miss it on my other computer which didn't have it.

Application and document launching is the vast majority of my usage of it. It is different from Spotlight in that Spotlight is good at searching inside of files. Quicksilver is much quicker at coming up with files with names similar to what you typed.

I also use it as a convenient dictionary. Bring it up, type a period, then the word I'm looking for, type tab, type 'dic' for the dictionary, hit return, and up comes the definition. The way I say it, it doesn't sound convenient, but it's very quick and easy.