First off, the following is a FRIENDLY responce to our disagreement. No offense meant or taken. Its allright to disagree. As long as you have come about it honest. By that, I mean you have made an informed decision, not something you herd or read or worse yet, that a friend of a friend said they did some such thing.
Tim,
This is fun, I like this, informed discussion... If the "picking of cherries" your refer to, is simply my wading thru the superfluous banter to get to the pertinent information, I am guilty as charged.

What your missing is I'm pointing out EVERY person quoted has acknowledged that 80Grain bullet of .243 diameter is a VARMINT BULLET. That's the plain and simple truth of it.
To be clear, I never once argued it would not work. Back to my famous analogy, so will my Ball peen hammer. But its use and the fact that it "would" work doesn't mean it should be used. Even though with me swinging it, I will absolutely, 100% guaranty its absolute effectiveness, accuracy not with holding.

As to the accuracy of said bullet. You know as well as I that every gun is different. My Ultra and the one we just purchased for a friends son shoot my load with a 100gr Hornady RN Very well. Mine to sub 1" and the boys sub 2" when he listens to his father.
Just so I have it clear, Tim. Your reason for quoting the 80gr is basically the lack of accuracy with the 100gr, IE it wouldn't/didn't shoot well?
Your spot on correct, a bullet THRU the boiler room will kill an aninal. My point is a VARMINT bullet may NEVER get that far!!! Even IF there was a CHANCE that a bullet would not properly penetrate, why chance it? We OWE more than it "could" work to the game we hunt.
In closing, The general consensus, from your own quotes, is that the 80GR IS a VARMINT bullet. No matter the context it comes from. That is all I am trying to get across.

Back on track:
Re: whats a good factory deer load for .243? This is my first season with the .243, so I'm not sure what to try in it. Any suggestions? Bullet types/weights?.
Buckslayer,
Any bullet of at least 90 Gr's weight, that shoots to your satisfaction.
I have had good luck with the 100 sierra loaded in Federal Premium.
I have herd others sing the praises of the 95gr Federal Fusion. But have no first hand experience with that load.
Tim says you have tried the Fusion, GREAT, let us know how it shoots and how it worked on deer!!
CW