As a writer (of grant proposals, many of which are not being funded in today's economy), I am a perfectionist, which often leads to the premature wear of the erasers on my pencils, which then tempts me into shouting expletives quite loudly while in the presence of coworkers. Relief for both issues has been found at last in the "shit" eraser.
Found at the Paper Source store (which is worth a blog in itself), this clever eraser is shaped like a smooth stone and fits in the palm of your hand, which makes it readily available when an inevitable f*ckup occurs. This product features one of my favorite curse words on one side and is easily turned over when the boss stops by for a more svelte, covert appearance. $4 at Paper Source. Also available in milder versions, including holy crap and oops.