Well, you usually cannot go wrong with Walter Matthau. He was a great actor - very versatile (comedy, drama, and did a good job of playing a "bad guy," as well as the "good guy"). Charade, The Odd Couple, Hopscotch, Grumpy Old Men, and Grumpier Old Men, etc.

Walter Matthau and Jack Lemon - in possibly their finest, most challenging roles - playing ribit and micro.