Excellent tool for visualizing garbage collection

IBM's PMAT (Pattern Modelling and Analysis Tool) is excellent for visualizing JVM garbage collection: https://www.ibm.com/developerworks/mydeveloperworks/groups/service/html/communityview?communityUuid=22d56091-3a7b-4497-b36e-634b51838e11.

It can parse logs with verbose:gc or Xverbosegc enabled on IBM JVM 1.3.x,1.4.x, 5.0, and 6.0; Sun JVM 1.4.1/1.4.2/5.0/6.0; or HP-UX JVM 1.4.1/1.4.2/5.0/6.0.