Ah Chocolate, the eternal quest. sigh.
I've tried 3 different "chocolates" from people selling Dekang liquid (litecigusa, cignot, heaven-gifts): all exactly the same, none of them tastes anything like chocolate. They taste like sugary perfume with a slight hint of a warm candy *scent* of something in the chocolate family.
MEH!
I ordered Chocolate and Chocolate Caramel from DIYflavorshack- again: meh. No perfumy taste but they taste like tootsie rolls, if you consider that chocolate. Angelique mentioned MyFreedomSmokes chocolate tasting this way as well, I believe because both companies mix their liquid using Lorann chocolate flavoring, which I personally don't care for.
Johnson Creek Chocolate is nicest so far I guess, though it's not exactly realistic. It's darker and a lot less sweet. Perhaps worth a try.
Nick (grimm) recommended thehouseofvapor.com goldlabel cocoa to me but I haven't gotten around to trying it out yet. He said it was a darker chocolate flavor- sounds promising.
As for tobacco- the closest I personally have ever gotten to an analog (I smoked Marlboro Ultra Lts) was when I was vaping a cart of Ecopure Regular and dripped a few drops of JC Original on the atty. I was surprised to find that once I'd found an analog taste... I no longer cared about finding it.
So I'd suggest getting a few different cigarette flavors (Kent, Marlb, etc) and mixing them by dripping to see if anything comes close.