Another cause of memory leaks is the MBeanProxy stuff.
Where the proxy gets stored against one classloader but references another.

One example, that doesn't actually cause a memory leak (because EJBTimerService is not hot deployed)
is the EJBTimer stuff:

public MBeanDelegate(MBeanServer server)
{
try

{ ejbTimerService = (EJBTimerService)MBeanProxy.get(EJBTimerService.class, EJBTimerService.OBJECT_NAME, server); }

catch (MBeanProxyCreationException e)

{ throw new IllegalStateException("Cannot create EJBTimerService proxy"); }

}