I like Debian, although that might change in time.
My first distro was Mandrake, but I didn't really like it... And it was hard to find rpm packages. SuSE is great as well, but Debian is my favourite, mostly because of apt-get and all the packages that are available. I'd like to try Yoper as well, and, in time, perhaps Gentoo. I've heard a lot of good stuff about it.