I honestly dont know where to begin. Apart from lounge access (where lounge exists), breakfast, water etc, I have also had good luck with upgrades (including some double and triple upgrades) as Gold.

Some of the better ones - full executive suite at Metropole (in case Jenbel reads this, no it wasnt that time I bailed on Up Over DO due to feeling sick), fulle executive suite at Petaling Jaya.

Australian hiltons are good for free bottle of wine (low-mid range) and chocolates.

Oh and Edinburgh Caledonian upgraded to Junior Suite with castle view.

Many other upgrades wont mention here - these are the best ones, until I made Diamond and double-upgraded at Conrad Singapore (that suite was bigger than my apartment!)