There's no sin that he won't forgive other than the one against the Spirit. Keep this in mind:
Check Revelation 14. If one receives the mark of the beast he will experience torment forever. No forgiveness.
There's evidence that to get the mark you'll have to deny Christ and bow to the anti-christ. That's the sin, not just having a tattoo on your hand. There are plenty of people today who are doing just that. Those will be the end days and it's a 1 time deal, a final choice before the grand finale. It's not the eternal sin described by Jesus in Mark 9, though.
