A kneadable (say: needable) eraser is the demented love child of a regular cheddar cheese pencil eraser and a stout wad of silly putty (tm). Used only by true artist(e)s, these wonderfully squishable exorcisers of error are usually grey-ish in color, and are indeed quite effective at what they do.

Their moldable, variable topologies gives them a succinct advantage over regular erasers, although their durability does (unfortunately) take a hit. Once, during chemistry, I sculpted ball-and-stick model complex organics using only toothpicks and a kneadable eraser. Stylish AND practical, as they say.

One of the primary physical joys of drawing cartoons, or anything in fact. Like a little lump of modeling clay with a nice smell that actually erases! Works better than your standard pencil-toppers, doesn't mess up your paper, can be reused almost endlessly, can be shaped into exactly the shape you need for it, and feels great to rip apart when your character doesn't come out looking just as you want it. Run down to your local office supply store and get ten of these things, right now! Why they don't recommend these babies to grade-schoolers I'll never know, except the probability they'd spend more time playing with them than slaving over their tests. God knows I had enough internal distractions working on those things that I sure as hell didn't need any external ones.