There are a variety of Nikon speed lights and I'm sure other brands that have adjustable settings and sensors that allow very nice control of the flash. These can typically be used with most cameras that have a normal hot shoe or pc plug with an cord. The cords are availble off eBay and other places.
The "ugly" look is typically just poor use of the tools or older flash units without the built in sensor and auto control.
The ugly stuff comes IMO mostly in two ways, 1- when too much flash is used so that there is to big a difference in luminance between subject and background and 2- when the shot printed too light.
It takes some practice but but done well it can make big improvements in many shots.
Get the book by Joe McNally "Hot Shoe Diaries".