What might look like diversified positions could be all one big trade. Think we should pool knowledge on possible uncorrelated trades out there. e.g Long Gold or Long Crude is really just a short dollar position as are many things out there. Other times less simple e.g. copper is going up on USD, maybe China, probably pulled down by US housing/reduced US import demand. What is going up or down that is not correlated with e.g. USD, US Indices etc.
don't think there are any un-correlated trades anymore. Ask the Pairs traders, ever increasing liquidity for similar gains.