Gentoo
...is a linux distro where everything is very customizable. You decide what to install and even how the programs are compiled. It's really satisfying to make everything work the way you want it to, but there is of course a downside to this.
If you don't have the time to wait for the compiling, you need a very fast computer. And to be honest, it can be a tough nut to crack when something goes wrong.
I used it for the first time in 2005 or thereabouts. (joined the gentoo forums under the nickname "kechara" Feb 23rd 2005). But having a, well by todays standard, slow computer I got tired of compiling things like kde, as it took more than one day!
Now I feel I'm ready to try again, and my computer is also better equipped to handle it 