I consider myself very fortunate to have been in a position to collect a few acoustics these past few years, and to have an expert luthier I can trust who works absolute magic. I've really had fun, also, cruising the music stores and playing everything I could get my hands on. I'd hate to have to pick one as a favorite, but I must admit I do have one.
Having really taken to the Taylor aesthetic over the years (dang, they know how to build a beautiful guitar), I was not impressed with the Guild F512 mirror black peghead, white binding, etc. when I saw it in the store. The guitar almost looked a little comical to me. BUT, when I played it I was smitten, and still am. It is my favorite guitar.
I talked to Strang a little before I ended up buying the thing -- lucky for me it wasn't in high demand and no one had bought it before it hit the 20% sale rack at the store. Strang probably has the most impressive collection of acoustic 12s I've ever seen, and I think he told me that the F512 was head and shoulders above the rest in responsiveness and sheer power.
Anyway, I know these big jumbos aren't for everyone, but there you have it.
I do have two guitars, which I've had most of my life; Barring dire circumstances, I will never part with them. The others would all go first, including the F512... The little red Favilla classical that I learned on was originally my mom's, and now ostensibly belongs to my 12 year old son (although I'm going to indian gift it at some point). My Ibanez AW-75 is still the finest mahogany 12 dread that I've ever played, and I bought that in 1981 with my own hard-earned money after saving an entire summer for it in college. This guitar is exceedingly rare, too, but nobody really knows much about 'em out there so they fly under everyone's radar screen in the collector's market. In any case, that's all irrelevant to me.
Final comment, I should mention that the F50RNT that I recently bought from Frosty has captured my heart in the 6-string domain, but in all honesty the 6 string is my secondary instrument. The Ibanez turned me into a 12-string player, and there I shall always stay.