The RPG-7 (commonly abbreviated to RPG) is a very simple yet very effective weapon that has embarassed superpowers (see Blackhawk Down), made bonfires out of armoured units time after time (see Grozny) and even now is taking a bloody toll on Allied soldiers in Iraq. It is straightforward, easy to use, cheap, battle proven, lightweight and has a wide range of ammunition available. Consequently there is absolutely no chance that the UK Defence Procurement system will ever make it available to the British squaddie.
On a lighter note, commonly used as a close quarter personal defence weapon by rebel armies and militia fighters across the third world. Also see the film 'The Beast of War' for a particularly funny scene where a mujahedeen fighter ND's with one.
Two Spam marines have been struck with these and survived. The round lodged in their bodies but did not explode. Both survived after each was operated on by a doctor, a nurse and a bomb disposal expert. One of the stories can be found here
Known to have a variety of munitions, from simple single shaped charge warhead to tandem anti tank warhead (40/88mm), thermobaric and anti-personnel grapeshot (think of a 40mm shotgun) Usually sport either iron sights or a PGO-7 2.8x optical sight that have built-in windage and rangefinding reticle, as well as 100m cross.
There's also a copy known as the Type 69 in Chinese service that have a folding bipod in place for the front grip.
All anti-tanks warhead self-detonate at a range of 1000m or so, however different manufacturers' munition may varies in term of accuracy, muzzle speed and self-detonating range.
Can be used in anti-personnel role under dire situation (aim for that wall behind the mujahideen, say) Can cause loss of hearing as well as bleeding ear when proper techniques and PPEs are not used.
Currently being supplemented and later on, replaced by the newer, meaner and more effective RPG-29 (66/105mm warhead instead of 40/88mm warhead)