I would consider Mitt Romney as the only "risky" candidate from among that tier. Rudy is simply poison, and McCain would simply be crazy.
If Fred Thompson were not in the race, I would consider Mitt Romney as the least odious of the candidates who seemed to have a shot of winning, though I am deeply concerned about what positions he would push should he win the presidency, especially in a second term.
It may well be that Romney's just as bad as Rudy, but simply hides it better. But if I have to support someone I'd rather it be someone who either at least claims to support my position. If that's not possible, I'd rather have someone who openly claims to be my enemy than someone who claims to be my friend but openly supports (supposedly on my behalf) positions to which I am opposed. Note that I'd be unlikely to actively support either of the latter two types of candidate.
As I see it, the primary front-runners are Giuliani and Romney. Of those two, I would consider Romney preferable. He has some points in his favor, though it's hard to tell how many; Giuliani has zero points in his favor to balance.
Of the next tier candidates, I would consider Fred Thompson to be likely the best. Duncan Hunter sounds like a good candidate, but I can't imagine any way for him to break through. Fred Thompson hasn't been doing well, but I don't see the systemic negatives for him that I do with the other candidates. The futures markets are down on Fred hard, but their predictive abilities at this stage in the game are dubious at best anyway.
At this point, I'm short on McCain and Giuliani, long on Thompson, slightly long on Rest-of-Field (Huckabee?), and neutral on Romney. That mirrors my desires, somewhat, but it also relates to how I see the systemic negatives. There are a lot of people whom I can't imagine voting for Giuliani in the primary under any plausible circumstance; he may well get a plurality of delegates, but I don't think that would get him the win.
Add in “Insane” John McCain for the trifecta.