Now that it's the holiday season, many of us are (hopefully) feeling extra generous, giving perhaps higher gratuity to busy servers working festive dinners and making sure to fill envelopes for our doormen, who can always be counted on to keep our secrets and sign for our (many, many) packages without judgment. It seems obvious, and mandatory, for most of us, but when it comes to some of the wealthiest A-listers on the scene, tipping seems to be a foreign concept. Here's a tip (pun intended): Don't be a Scrooge like these celebrities.