I have been rather lucky when it comes to my holy grail.

Fortress Maximus, thank goodness for encore
Bumper/Bumblejumper, I managed to get it for $100

My next holy grail, is the complete G1 collection which is only 5 figures away. After that it will have to be X-9 Jaguar
Then SG 2008 Box set (only need Op, SS and Jazz)