One suggestion that has gained popularity in the post-crisis regulatory debate is a tax on financial transactions.
Proponents suggest that the tax would raise revenues for governments (at a time when such revenues are badly needed) and curb the excessive speculation that contributed to the global financial crisis.
In August 2012, France became the first eurozone nation in the wake of the financial crisis to implement such a tax, and so far, it's been a total failure.
Source: Business Insider. Read full article. (link)