The last F&%ing manifold bolt!

If you rounded the bolt that badly trying to break it loose, let if soak in penetrating lube for a couple of days- give it a good soak and gently smack it with a hammer (just to set up vibrations so penetrant can soak into threads) every day for a couple days, then go the drive a socket on it route and back it out. If you twist it off, you'll learn a whole lot of new expletives (trust me on this one...lol)