Hey, man, happy birthday!

My gf turns 21 on Oct 4, when's yours?

Hmm... "dark" beers... These guys have suggested stouts, which are often a good choice if you're not really a beer drinker, but they can be a little filling.

You may want to look in the direction of a brown or mild (Newcastle being a classic example; Pete's Wicked probably fits into this category as well).

Porter might be a good option, as well. Porter tends to be a lighter version of a stout ("historically" it's a pale and a stout blended together, like a black & tan). Porters tend to be a little roasty, but if you're a smoker, you might like that flavor.

Completely out of left field, you may want to try a Wit (White), weizen, or hefeweizen (wheat beers) might be a good call. These beers are completely hit or miss, but a lot of people that "don't like beer" tend to like hefeweizen. Hoegaarden and Blue Moon Belgian White are easy examples, but anything that has "white" or "wheat" or "weizen" in the title works.