Just chiming in to second the praise of Tichu: the rules just feel so well designed with their careful blend of systematic regularity (everything adding up to easy 100s, no asymmetry between the for colors) and convention (most new players already know the combinations from poker) that is balanced by just the right amount of occasional chaos (when too man hands align into "bombs") and arbitrary detail (the bird and the dog, two of those specially marked jokers) to spice things up. Everything seems to have a purpose, whereas the arbitrary elements of evolved rulesets of traditional card games often seem somewhat random to me.