In the 5 years since the USGA (United States Golf Association) first allowed GPS devices on the courses, there have been major advancements in the technology. The number of GPS units has increased as well, and depending on the level of detail and accuracy needed prices can vary.
GPS City , experts in GPS related hardware and software, recommend golfers check out the Garmin Approach G3 or G5 models. These fantastic units offer full color touch screens, rugged waterproof designs, and thousands of preloaded courses. Both the G3 and G5 include mapping of the US, with Canada available via download. The Canada maps are quite rare, since many other companies either don't offer them or have very limited coverage. A slightly smaller screen and lower resolution on the Approach G3 are what differentiate the 2 styles.
If a basic device is your preference, the Golf Logix or Golf Buddy systems may be in order. These feature sunlight-readable monochrome LCD screens, at least 14 hours of battery life and internal memory for course downloads. These entry-level units don't offer preloaded data, but the course info can be accessed via their respective websites, Golf Buddy.com and Golf Logix.com.
USGA professionals have used Sure Shot Rangefinders in the past, but will most likely upgrade to one of the newer models available. Garmin, always a leader in the GPS market, has taken the Sure Shot functionality and added the necessary features to aid everyone from beginner to expert.