Siege tournament. (Make it a League level Tournament for a single day, at the beginning of a week so it doesn't impact the weekly ranking contest? I can imagine the screaming that would come from the ranking's players on this though.)
Raid tournament. (League total raids? There is already the weekly rankings for the solo player score)
Trade tournament. (Do you mean on the market, or directly? and would that be for total, or number of trades?)
Spend your sapphires tournament. (LoL! but I thought that was what the Fortress's were for?)
Darkening tournament. (Leaves too many players totally out, would only benefit the large beacon leagues)
Summon wraiths tournament. (This has potential, but it would have to be a League Tournament - there is a limit to how many wraiths you can summon daily, and you can only have 50 yourself unless you've researched that in the Obelisk. It would be one way to increase everyone's Friend count)
Collect tribute tournament. (Already part of the weekly rankings for solo, would have to be League?)
Free giveaway of your food to Lord Oberon to stop the famine tournament. (If you're not at a negative food production rate, you're not recruiting hard enough, so bring on the famine!)
Spy tournament. (This has potential, even small players could get in on this - and just think about all the fun this could stir up!)