I was going to say IPA or IIPA, but, for the rest of my life? A little lower alchohol means I could drink more without passing out when I was older. So a good, hop bursted and dry hopped American Pale Ale!
I know it's going to be the popular answer, but I'm going with IPA as well. It's crisp and refreshing enough to be a good summer beer, but hearty and warming enough to also be a good winter beer. Perfect for all seasons, really!
VERY tough question. I do think that it appears IPA is winning, and I'd have to go with that too...if it was one particular recipe, I'd have to say a nice hop juicy west coast style IPA. But think about it...if you're just limited to a style, IPA does give you a wide variety of flavors...you could even make a stretch and include some "black IPA's."
Edit: Or even think about the variety you can add with yeast choices...I love Belgian IPA's too!
I have to agree with the APA. Because of the ludicrous premise of the question, I have to take many things into account. Are there any beers that I have gotten sick of at any time. Of course there are. On some occasions I can't bear the idea of an IPA or Weiss, and on hot days a Stout seems like torture. Taking everything into account, a solid, moderately hopped APA is the perfect anytime beer.