was combinatorics part of discrete math? i forget. anyway, if it is, i find the variations on n choose k very applicable and ridiculously easy to program (b|c it's just an equation f(n,k)) so you might try something with that. the odds of getting a particular poker hand, or the odds of getting a straight. or have the user put in 5 cards, # of players, etc and calculate the odds of getting those 5 cards. just throwin some stuff out.