Heavy, dense, to dampen vibration. Shortening the throw obviously increases the effort.
I had a Team Voodoo knob, but have settled on a nice Japanese teardrop; its quite heavy (no idea what the metal is), but gives a nice throw action, precise like a SMLE, because the throw isn’t shortened. And I like the appearance. The shift lever is polished (or the top is), and I have used a tight fitting O-ring to push down the leather boot a bit.