I believe someone suggested loans collateralized on stock and other such speculative assets be taxed as realized gains, which should go a long way to stop the absolutely mindbogglingly obscene displays of mega wealth we've been seeing as of late.

As for income, there should be nominal brackets established at the 20th, 40th, 60th, 80th, 95th, and 99th percentiles of income for a given year, with 20th, 40th, and 60th percentile income taxed at the percent of national wealth each of those brackets owns, income in the 80th and 95th brackets being taxed at twice their respective shares of the national wealth, and income above the 99th income being taxed at three times their share of the national wealth. Then have a half a percent multiplier for every multiple of twenty times the median income of the 0-20 percentile bracket an income crosses.

Doesn't just tax the rich, it directly incentivizes them to spread the wealth to lighten the crunch on their top dollar. The rich literally can get their own tax cuts by not hoarding wealth.