A lot of the two-character TLDs are already associated with countries.

The .ng extension is Nigeria's, and goes for a whopping $50,000 per year. [1]

The .ay TLD belongs to Adygea (a republic within Russia). [2]

[1] http://www.101domain.com/ng.htm

[2] http://nationstates.wikia.com/wiki/.ay

Edit: Formatting