If you are a fan of BIG beers. Let me suggest the mother of all pumpkin beers, Avery's pumpKYn. I try to land a few bottles every year. It is expensive, but it is not the type of beer one drinks several bottles of. Each year, the ABV sits around 15 to 16 percent. I like to say that this is the pumpkin beer that should end every other breweries' attempts to craft a pumpkin beer. They should all stop and deem Avery the winner. It is not just a little aroma of pumpkin, it is a mouthful of thanksgiving with each sip. This beer is heavy and creamy and fills your nose with nutmeg and cinnamon. Skip a meal for this one, it will fill your stomach.
If you want to explore a wonderful variety of this brew. I would suggest Avery's RUMPKIN, which is their pumpkin ale aged in rum barrels. This is a bit more of a kick in the mount though, as it not only get's a great deal of sweetness from the rum, it also gets a bit more alcohol too. Rum barrel aging is a unique process. So you get to try something that is likely new to you. So often, brewers use other spirit and wine barrels, but you do not see as many use rum or tequila barrels. Kudos to Avery for that.
Both brews are priced around 10 bucks per 12oz bottle. And you will need to shop at a specialty store for them. I occasionally see them in Schnucks in Saint Louis though (which is a grocery store). They are pretty rough when they are fresh. So I like to grab a stock each year, then drink the ones I purchased the year before. Age them upright at cellar temps, IN THE DARK. I can not stress that enough.
Hope you enjoy them.