Hi torroray,
Equity index futures are popular, the FTSE 100 and DAX being obvious choices during the European session. The U.S. markets open at 2.30pm U.K. time so, if that's convenient for you, it might be worth looking at e-mini futures for the S&P 500, Dow and Nasdaq. On top of these of course there are commodity futures, currency futures and universal stock futures etc. Which of these will suit you best - if any of them - is hard to say without having a good insight into your trading style and objectives. For more general info' on choosing a market and instrument to trade, check out this FAQ;
Which Should I trade - Stocks, Futures or Forex etc.?
Let us know what you decide!
Tim.