Spotlight pop-up effects
It sounds to me like you may be describing Quicksilver, which is, among other things, an application launcher.

http://qsapp.com/index.php

I use it daily and it can look very much the way you have just described.  It has several different interfaces.

However...  It is definitely not spotlight, and it doesn't use any spotlight like icon...   

Mine also pops up in the middle of the screen, not the top right like spotlight....

Does this sound like what you may have been looking at?