I'm fond of doing traditional stuff like a pumpkin beer for the fall. You have the added benefit that if it isn't all consumed by Halloween you can save it for Thanksgiving and even Christmas because of the spices. Chocolate beers are also fun if you have a sweet tooth, as are coffee stouts. Chocolate beer is a bit tough if you're doing it for the first time because you don't know if it'll have too little or too much chocolate flavor. For this I'd recommend just sticking with a recipe that you find at a homebrew store or online retailer, because they tend to be conservative when it comes to adding chocolate. Then you can slowly bump it up or down to your liking. Just some things to think about.