<I>The Apartment</I> is easily my favorite Wilder; one of my top favorite films, period. I'll watch it whenever it's on.
I just saw one that's a bit of a rarity, <I>Ace in the Hole</I>, which is about the media culture, basically. It's pretty good, with an unyielding performance from Kirk Douglas, but I feel like the criticism in it isn't quite on the mark. Great film though, without a doubt.