Frankly I don't have any respect for any of them.
Giuliani has already proven beyond a shadow of a doubt that he is even more willing to ride 9/11 into office than even Bush was, going so far as to admit outright that he believes this is a "one issue election." He then proceeded to blame Clinton for the lack of any kind of meaningful response or preparedness after the first WTC attack, handily ignoring the fact that, while it is true Bill was President at that time, Rudy G was the friggin' mayor or New York...and did nothing. He didn't even replace the radios that his Fire Chief specifically told him did not work in the buildings...
Romney? Hell, he may be a decent guy, but I don't want anyone with that level of religious devotion in office, especially not someone who belongs to a cultish, heavily-centralized authority mystery religion that requires their adherents to wear special undergarments and promises them godhood in the next life. I just don't want that guy's finger on the proverbial button.
McCain used to be someone, but then he sold his testicles to GWB. He reversed himself on nearly every position he ever held that was contrary to the Bush party-line after the '04 election, and with it he lost any credibility he had.
Fred Thompson? Oh, please, haven't we had enough of the Presidency being a friggin' entry-level position? Just because you recognize his face is no reason to vote for him. Have you checked his record as a junior Senator? I can sum it up in one word: "non-existent."
Ron Paul? Sigh. Paul is not the Great White Savior of the Republican Party. Although I do like his record of respect for the Constitution, and he is the least objectionable of the individuals mentioned, in the end he's just another damn Republican from bloody Texas, and I've had enough of them, thank you very much.
I'm tired of Republicans. I don't trust 'em, no sir, I do not. They have lied to me and mine far too much in the past decade for me to trust 'em. (Of course, I don't trust any politician all the much, I'm not terminally foolish after all, but at least the Dems haven't told me any lies that have resulted in the deaths of more than 3000 American servicemen and women...)