I don't know what my fastest is. Slack's fast enough for me. But recompile your kernel for the minimum support and turn off all unneeded services. The thing that takes the longest is dhcp so, if you only want to rock and not surf, get rid of stuff like that. My theory on boot times is that never rebooting is the fastest boot.
Of course, I just had to reboot yesterday to make sure a problem I was having wasn't system-specific, so that's not always possible.