Forex Trading
If you do long term investment in forex it is definitely allowed from islamic point of view. In the short term like exceuting trades in hours, minutes or days etc, you are not doing anyone a harm but participating in a game where things are almost random. But in the short term the issue is that you have to be very very skilled and smart players otherwise the big sharks will eat your lunch and you will lose the money. So for your own financial safety and well-being islamic principles led alteast me to think that if you are not highly skilled and learned from a good trader company or institute, your participation in such a market would be against the Islamic principles.