Chocolate is considered most appropriate, especially from an expensive, foreign brand. And perhaps it is a universal truth that nothing says I Love You like a box of exotic chocolates from an exclusive French boutique that the guy has never heard of.
Japanese burger chain, LOTTERIA, is going to start selling Tsuke-pote (meaning "dipping"-"potato" in Japanese) on January 9th. Tsuke-pote is french fries with chocolate sauce for dipping. It will be sold for a limited time only from January 9th through mid February.
It probably tastes like chocolate covered pretzels or potato chips, but it should be a bit more greasy. Just by imagining its salty-sweet flavor, it makes my mouth water :)