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