In case you haven't heard, the cellphone celebrated its 40th birthday this past week. In its brief lifespan, the mobile phone has had an enormous impact on human society, including in developing regions where the personal computer remains prohibitively expensive. How big of an impact? There are 6.8 billion mobile cellular subscriptions worldwide this year, according to the United Nations' International Telecommunication Union. To put that number in perspective, that's nearly as many subscriptions as there are people on earth (more than 7 billion). Of course, this doesn't mean that cellphone technology has reached its limits of innovation. Far from it, in fact. Those of us who live in areas with so-called advanced 4G LTE mobile networks still suffer from the occasional dropped call, spotty reception or poor audio quality. The mobile industry can do better, which is precisely what 85-year-old Martin Cooper, the retired Motorola engineer better known as the "father" of the cellphone, said in an interview last week with the BBC. The technology exists to improve coverage and capacity of cellular networks, but wireless carriers thus far have focused on speed instead, Cooper opined. Although the cellphone was invented in 1973, it didn't emerge as a viable commercial product until the 1980s. Early mobile handsets were expensive, heavy and bulky; they were luxury items enjoyed by the privileged few. There's an iconic scene in the 1987 film Wall Street where ruthless corporate raider Gordon Gekko, standing on the beach in his bathrobe, is chatting on his 2.5-pound Motorola DynaTAC, the first commercially available wireless phone that cost a cool $3,995. At the time of the movie's release, the scene conveyed Gekko's wealth, power and arrogance: "Wow, he's on the beach, talking on a phone ... with no wires!" Twenty-six years later, the massive, shoe-sized DynaTAC looks laughably oversize and about as technologically advanced as an 8-track tape player. And with the majority of the human race now possessing smaller, cheaper and far more capable mobile phones than the one used by the diabolically greedy Gekko, the device's elitist aura is a distant memory as well. The cellphone went mainstream in the '90s, and manufacturers began rolling out a wide variety of handsets designed to be both functional and fashionable. In honor of the cellphone's 40th birthday, we've decided to spotlight the best and worst mobile phones from the past two decades. You might have used one or more of these phones in its heyday. Others you might have forgotten -- or wish you had.