APX4000, XTS1500, and sometimes a Realistic/Radio shack handheld scanner......like others have posted, clipped to the passenger seat seatbelt, or in a slot made for cell phone or iPod. Some cars with iPod/cell phone slots fit perfectly for handheld radios. One of my cars has a nice and tight area for this near the left lower dash, and the antenna is even out of the way too. Make sure it is secure, I have also seen many injuries from radio equipment, weapons, magazines, and other loose items being problem.
Some die hard "radio whackers" should wear a helmet when in their vehicles, as they leave things loose, or trust Velcro for their mounts.