Means testing at various thresholds, Chained CPI, handful of Cap increases. In this figure a score of 0.6 means entirely backfilling the 75 year actuarial gap. (For those who care that is percentage of GDP). Note that if you set means testing levels at 'rich' levels you don't really get much bang and same for donut hole proposal for cap increases (e.g. the Obama-Biden 2008 proposal to partially lift the cap only for $250k+ folk).
Over to you all, I just like starting from real data points.
Source: CBO 2010 'Social Security Policy Options'