Pence, Tancredo and Newt are good, but I don't know how strong they will be in the general election. Hunter is weak on fiscal issues and trade, and Huckabee is a full-blown tax-raising cigarette-hating RINO. But I will vote for anyone who favors the WOT.
As for deal-killers, what would you do if the election was between these two candidates?
A conservative who is pro-choice (and conservative on all other issues)
A liberal who is prolife (and liberal on all other issues).
I would vote for the conservative.
I can't imagine a true conservative who would be pro-choice, so in the scenario you give, I'd vote third party, or something other than a vote for either of the two you mention.