As far as becoming adept at Linux goes, I recommend Gentoo or Slack. Gentoo is my favourite distro because everything is up to me. I can easily create a powerful, yet streamlined fully customized system according to my needs. The community is unparallelled too, as is portage.

No desktop environment is installed by default (you have to do it yourself, but that's as easy as "emerge kde") so it definitely doesn't focus on eyecandy, but the option is always there (I have Beryl installed, and it's great. ).

The LiveCDs/DVDs are fully functional and I haven't had trouble with the few that I've used, though I usually do a minimal install which is a massively cut down LiveCD without a DE, etc.

Slack is a little more difficult to use, but mostly it's the same kind of principle as Gentoo. It's definitely a developer's distribution and is known for being rock solid in terms of stability. I used it for a little while, but I didn't really like it as much as Gentoo though, so I went back.

As far as buffer overflows go, any distro is as good as the next unless you want to exploit overflows in the distribution itself, since they occur from poor programming practice. Why do you want to play around with them anyway?