Nothing music wise...but the guys signed my copy of Lifting Shadows the last time they were in Melbourne.
Also the print that came with the BC&SL Box Set was also signed by each member of the band including MP!
A framed signed Tour date announcement of the Systematic Chaos Tour dates for Australia by Roadrunner which is great,
because it was their first time in OZ! (apart from G3 in 06)
It has an authenticity certificate but it still may be one of many but still great for me.