I've been fooled be a few of those, even rotating wall clouds with scud close to the ground. In general, I agree with akuter - I get as far away as possible and let the NOAA folks worry about the classification.
Cold Air Funnels are completely unrelated to tornadoes... They are similar to waterspouts over the Great Lakes / oceans. They do NOT form with thunderstorms, but with large cumulus clouds. Very rarely do they even have precipitation. Once in a blue moon one does hit and has 40-50mph winds, but far and away most are just pretty to watch.
last summer i video'd several cold air funnels from my balcony. they really looked like tornados. there was several one after another. funny thats where they were seen a few yrs ago. maybe terrain part of the factor. anyways i was shocked to hear tornados on the scanner. looked at the radar and was like there wasn't even a storm on there!!!! that's how you tell a cold air funnel from a tornado. if it was a tornado there would be some scary stuff on radar. funny thing is our town went ahead and sounded the sirens. everyone in this county and adjacent was freaking out at first.
Cold-Funnels have formed three at a time at the mouth of the Chesapeake Bay. They do touch down, and could capsize a small vessel, as well as do minor damage when they come ashore which has happened.
A tornado is NOT a tornado when some idiot doppler-weather operator at local tv stations cry wolf everytime they interpret rotation in a thunderstorm. In Hampton Roads VA (viewing) area all three tv stations have made these false alarms dozens times since they obtained doppler radar. In my memory they have been wrong 100% of the time. The few real tornados we had showed no rotation on Doppler, which means either idiots designed the software, idiots operate it, or both.
It used to be that only when a public safey officer or certified spotter called in a tornado on the ground was an actual warning sounded. Back then a Watch meant something, and a Warning meant run like hell, right now. Nowadays the NWS and tv stations have dumbed-down the Warning to useless babble that interupts tv programming and rarely ever coincides with an actual tornado. Nobody pays much attention to Warnings anymore and you can't blame them when the alarms are always false.