Heliotrope is a creamy, almondy-smelling flower. It is purple in color. It provokes the same love-hate reaction that amaretto-type scents do, because it's really very similar. Here's a link to what wikipedia has on the subject:
As far as scents that contain it...
I know that Etro has a very nice Heliotrope-scented candle. You can find that at a lot of boutiques.
For mainstream, you can also find Heliotrope in Gucci II EDP, Valentino V, Gucci EnvyMe2, and Miss Sixty.