Remember the flywheel tool.  Also a cheap 19volt impact is nice to remove that sucker quickly.  What you bring is also dependent on your riding area.  Hard terrain, mud, sand, they all would have a tendency to loose/break different parts.

I ride 100% sand, so extra bars are not required (soft rollovers typically).  I always have different main jets, second sprocket, second chain, extra clutch, brake, and shift levers.  Extra clutch and throttle cables could be useful.  I have a full set of spare electronics too.