There's also Klimt's famous work, which is nearly as cliché and corny at this point. Alas.
For those who've never been, I do recommend the
Neue Galerie up on Fifth Ave/East 86th if you're interested in early modernist art & design. They have quite a varied collection considering the specificity of their mandate (Viennese & German works, circa 1900) all housed in a majestic old building that's just as much on display as the art is. A+++