I got a box of .22 WRF today (also known as .22 Special); it's almost an obsolete cartridge, as only old rifles are specifically chambered for it. Now, they still make ammunition for the old weapons and also because it can be fired in .22 Magnum weapons without problem, and it's not that expensive; about 3 times the price of .22 Long Rifle and half the price of its offspring cartridge, the .22 Magnum.
Personally, I reckon the .22 Special should have been what the .22 Long rifle is today; it can push a 45 grain bullet at a modest but still respectable 1300 feet per second, which is in line with the most advanced .22 Long Rifle rounds in development in regards to energy on target. If it took off, it would have been the same price as the .22 Long rifle is today, but with better ballistics (a little better).
It just looks better too, with much of the bullet in the case, rather than the odd looking .22 Long Rifle rounds (it also doesn't look long and skinny like the .22 Magnum rounds).