Sometimes it's the little things that make us smile. We first picked up Propaganda's Help! drain stopper so that we could use our too-old-to-have-a-working-stop bathtub, and later discovered it also fits perfectly in our kitchen sink drain, providing a leak-proof plug superior to the generic metal ones that were here when we moved in.
The hand reaching out of the middle makes for an easy-to-grab handle when you're ready to drain the water, and the drowning person allusion is guaranteed to please kids of all ages. We picked ours up locally, but they're available online from SeeFred.com for $4.50.