A cult favourite flavor of the famous energy drink Gatorade that has a light, fruity taste and a pale purple color. It's one of the brand's lesser known flavours and it's still available in certain places under the name Frost Rain Berry.
Basically, it's just something rare to find.
Boy: you're like rainberry, prettyepic and hard to find.
A person you hate intensely not because they deserve such hatred but because they serve as a focus for your general hatred. A healthy way to dispense with excess animosity.
Jake's not really that big an asshole. He just serves as my hate sink.