Funny tip jars are a great way to squeeze every last cent out of people at any place of business that underpays employees as much as it overcharges customers. When creativity is pretty much at a standstill at any job that requires tip jars, creative ones often not only provide workers with an outlet, but also give customers a smile... and a reason to actually use the tip jar.
Pictures of these jars are all over the web. Instagram even has a hashtag called #tipjar, and that's just the singular one - you'll also find #tipjars, #tipping, #baristas, and plenty of others.
Lots of tipping jars (or whichever receptacle any restaurant, coffee shop, or otherwise sets out for tipping) use a brilliant tactic: making it a tip jar contest. For example, they'll label one jar "Batman" and another "Superman," or they'll pose a question like, "Who would win in a fight, Wolverine or The Hulk?" People vote with their dollars, so the venue offers a visual public consensus, and all the awesome, hardworking employees get more money.