In my opinion, the all-time greatest bassline Flea has played:  Subway to Venus off of Mother's Milk.  Heck, he smoked it through that whole album...it was back when his tone was more scooped out and less dirty.  Cool stuff.
 
Will

My Favorite FLEA bassline is Soul to Squeeze
 
Very simple.  Totally in the Pocket.

I love the bass line in Soul to Squeeze.  Aeroplane's solo is also really cool.

Check this out...
 

 
Shot during the Mother's Milk tour and they were ON FIRE!