Add me to the list of people who will find it difficult to say no to an officer, but will refuse consent.
Back when I was young and naive I was asked twice and gave consent both times because, like many of you, I have a lot of respect for cops and the job they do. Now that I'm older and wiser, I will politely refuse consent if asked. Of course, I no longer have the hotrod and long hair that prompted the officers to go fishing :)
A couple quick thoughts on some of the issues brought up. For actual legal analysis, you'll want to consult a lawyer - but here are a few things to consider.
About the warrant issue - as gigag04 mentioned, there are several situations where a warrant is not required for a search to be legal. And even in cases where a warrant should have been required, the evidence can often still be admitted. So don't get too hung up on warrants. Demanding one won't help your case any more than simply refusing consent.
Someone asked about waiting for a K9 to arrive after they have refused consent. Typically, a K9 walking around the outside of your car won't be considered a "search" under the 4th amendment. So if they can do that while they have you stopped for a legitimate reason, then you don't have a complaint. If they detain you longer than the stop would normally take so that the k9 can get there (without probable cause), then it is an illegal seizure (of you and your car). How long can they keep you there for the traffic stop? That varies by court... but as little as ten minutes has been held to be unreasonable.
On a related note. When I went to the local "junkers R us" to buy my daughter a car for her 16th birthday, I was concerned about anything that might be left in the car. I asked nicely and the local PD actually ran their K9 through the car for me. I made sure to let my daughter know that since they had cleared it, if anything was ever found, she didn't have an excuse!

Not sure how many departments would be willing to do this, but it can't hurt to ask. I started with the community relations officer for my area - that probably worked better than just calling the station.
NRA Endowment Member. Texas LTC Instructor. NRA certified Pistol & Home Firearm Safety Instructor - Range Safety Officer
Any comments about legal matters are general in nature and are not legal advice. Nothing posted on this forum is intended to establish an attorney-client relationship.