I humbly suggest going everywhere. Get a one month train pass for Europe. Then take the trans-siberian railway across russia. Drop down into Asia through mongolia and china. Wander around southeast asia. Pop across to Africa doa bit of tomb raiding and safara-ing, then head over to south and central america. Do not miss the opportunity to go to CUBA whilst Fidel Castro is still alive. Finish up by driving around the U.S and Canada.
I haven't mentioned Australia or New Zealand becaus eyou can do them for a year each on a working holiday visa once you've finished uni.
N.B I should pount out that I have done very little of the suggested itinery...it's just the one I WANT to do!
Have you got a year? If so, do south east Asia. f***ing amazing.
I had a month in China, then a month in Thailand, month in Laos, six weeks in Vietnam, a month in Cambodia, six more weeks in Thailand, a month on mainland Malaysia, a month in Sarawak (Borneo), a month in Sabah (Borneo) and a month in Indonesia. Finished off with three weeks in Australia. Amazing trip and not that expensive, cos in some countries you can live like a king for less that a few quid a day.
How about the London Underground? Every other f***ing gap year tosspot seems to be on there. Don't forget to leave your stupid great backpack on your back so you take up twice as much room and knock people over every time you move......