What is your client surprise budget?
Kathy Sierra has this wonderful post on the Creating Passionate Users blog. She gives several examples how businesses have made their products and services "playful."
Surprises are one of the best things you can do -- psychologists claim that intermittent rewards can be more engaging than consistent rewards. Remember, surprise=delight.
I worked for a guy who ran an exclusive, foofy, insanely expensive health club. He took 100% of what should have been (back then, when Ads were King) his advertising budget, and instead put ALL of it into a monthly "member surprise" budget. Nobody ever knew what was going to happen. You'd be in an aerobics class with 100 people (it was a big place), and as you walked out, suddenly there were carts loaded up with bowls of frozen yogurt and a toppings bar. You're in the weight room when the employees start walking through handing out exclusive t-shirts, always with his logo, and always with a fun quote, that you knew would never appear on a t-shirt again. Members collected these things like rare beanie babies. The late-night exercise classes were the hardest to fill, but he would take the worst time slot and make it interesting... the 9 PM folks might walk out of class only to be handed a wine cooler or even a relaxation CD.
It always felt like a party in there! And employees fought over the chance to be the one who got to hand out the cool stuff. And there was no hierarchy in deciding who got to do that...everyone from the janitors to the office bookkeeper might be "picked" to be the hero. I had never before, and never since, seen the kind of loyalty among both staff and members that I saw in that place. His attrition rate for both members and employees was less than half the industry average for health clubs at the time.
Thanks to Johnnie Moore for the link.