Need some serious help!!!!
 

I have 12mm, open ended lug nuts and was taking one off and the damn lug nut split!!! Any ideas of how to get it off!!!??? Thanks.

can u take a pic of the problem?

+1 for pics. We would need to see the problem in order to help you properly.

Don't have the camera now. It is a lug that has a key that goes into the lug, not on the outside. Like a 12mm allen wrench. Hope this helps.

camera phone?

What if you tighten the other four nuts, leaving enough play in the broken one to get off with vicegrips. How cracked is it? Can you crack/split it more and just break it off?

Vice Grips FTW.

You can try a Gator Socket.
http://www.endeavortool.com/admin/files/ggrip_20.gif

That sounds fucked to be honest. Proper fucked. Might be time to go buy a cheapie socket that's slightly smaller than the lug nut. Pound that shit on there with a deadblow hammer and remove it as usual. It's worked for me in the past.

When all else fails, brute strength and ignorance prevails.