Shoulder fired rockets (like the Russian RPG or U.S. LAW and AT4) are very commonly encountered on the battlefield. That's because these things are cheap and very useful. The Russian designed RPG series is the cheapest, which is why the about 55 percent of these weapons are of the RPG family, but account for only about 45 percent of the money spent to buy them. The more expensive Western models are more effective, but more expensive.
Less wealthy armies the world over, including irregulars, love to use their Russian made RPGs (Rocket Propelled Grenades). The RPG evolved from the World War II "bazooka" type weapons and was introduced by the Russians in 1961. The current RPG 7 weighs about 17 pounds, with most grenades weighing five pounds each. American tanks and M-2 Bradley infantry vehicle (with additional appliqué armor) are mostly invulnerable to RPG fire. During the Iraq fighting, it was common for most of the armored vehicles in a unit to be hit at least once by an RPG round.
The real damage from RPG fire was the fragments from the exploding grenades. Even the anti-tank round (the most common fired by the RPG) would throw out wounding fragments for 10-15 feet. These rarely killed, but troops were often wounded in the arms, legs and face, and often put out of action for a while. But most armies, and irregulars, like the RPG because it is cheap, easy to use and very effective against troops lacking protective vests and helmets. The RPG is also effective against many other armor vehicles. Most RPG anti-tank rounds can penetrate 12-20 inches of ordinary armor. But most modern tanks no longer have ordinary armor, which is why the U.S. M-1 tank and M-2 infantry vehicle can take an RPG hit and keep going.
The RPG launcher costs anywhere from $100-$500 (lots of second hand stuff out there.) The most common RPG ammo is the anti-tank rocket and these go for $50-100 each. Costs add up, however, as you have to fire a dozen or so rounds to develop some accuracy. Unlike the launchers, RPG ammo doesn't get cheap, unless some wealthy nation is flooding an area with it, because the ammo gets used up and the launcher does not. Without much practice, a user can hit a vehicle sized target most of the time at ranges of 50-100 meters. As an operator fires more rounds, he becomes capable of hitting stationary targets at up to 500 meters, and moving targets at 300 meters. It's this last skill that has made the RPG dangerous against helicopters.
Irregulars also like using the RPG as a form of artillery. Get a bunch of RPGs firing at the same area say, a kilometer away, and you will do some damage to any people walking around. The rather more rare (and expensive) anti-personnel RPG rockets will spew out fragments up to 30 feet or more.
The RPG-29 is the most common recent development of the RPG line. It entered production just before the Soviet Union collapsed in 1991. It is available through legitimate, or black market, arms dealers and is more expensive than the RPG-7 (which is manufactured by many countries.) RPG-29 launchers cost over $500 each, and the rockets go for about $300 each.
With a ten pound launcher firing a 14.7 pound 105mm rocket, the RPG-29 warhead is designed to get past some forms of reactive armor (ERA). The larger weapon (3.3 feet long when carried out, six feet long when ready to fire and 65 percent heavier than the 85mm RPG-7) is more difficult to carry around and fire, but has an effective range of 500 meters. The warhead can also penetrate five feet of reinforced concrete.
Meanwhile, troops in the West had to improvise a bit. After September 11, 2001, the U.S. military revived an obsolete, four decade old anti-tank weapon because it was a cheaper, and more portable, way to provide the infantry with some portable artillery. This is the LAW (Light Anti-tank Weapon). These 7.7 pound, one-shot (the launcher is disposable) anti-tank rockets were a replacement for the World War II bazooka (similar to the Russian designed RPG). However, by the 1970s, it was obvious that the LAW was not able to kill most modern tanks, and in late 1980s, was replaced by the AT4. However, the heavier (15 pounds), and more expensive AT4 ($2,700 per each disposable launcher and four pound warhead) is also larger (40 inches long and 3.3 inches in diameter.) Since American troops rarely faced enemy tanks, but did frequently need some additional firepower to deal with enemy infantry in bunkers or buildings, the AT4 was seen as a step backwards.
The LAW has several advantages. It is compact (20 inches long, 2.6 inches in diameter), light (7.7 pounds) and cheap (about $2,000 each). Its 2.2 pound warhead can still knock out light armored vehicles (and unarmored ones as well), but it most often used against enemy troops inside bunkers and buildings. For that job, the U.S. Department of Defense had bought the SMAW (Shoulder-Launched Multipurpose Assault Weapon). This was a 17 pound Israeli design (in response to the RPG). But the SMAW launcher costs $14,000, and each rocket costs more than their RPG equivalents (and are a bit more effective.) Actually, many troops have expressed an interest in just getting the RPG, which has a larger (6 pound) warhead, and is a lot cheaper (the RPG launcher goes for about $500 each, brand new, and the more advanced rockets can be had for under a hundred dollars each). However, the compactness of the LAW, and better accuracy, does make a difference on the battlefield, and is considered worth the cost. The LAW is simple, light, easy-to-use and relatively cheap. Its hard to improve on that, which is why the LAW is making a comeback. Actually, it never went away in many other armies.
But the king of bargain-basement, but effective, infantry artillery remains the RPG-7.