I guess I don't really have much for grails, since there is so much I still want that it would be a rather lengthy list.
However,the closest thing would be the LEGO UCS X-Wing, as it, along with the 3 japanese mini sets, is the only LEGO set I'm missing from having pretty much every single set put out to date.
There are never many on ebay at any one time and they usually run in the $150-$200 range for MIB sets, which is what I'd want. I'd rather not take the chance of missing pieces on loose sets. So I'll just continue on having a 99% complete LEGO collection for the time being.