The gg cctld allows single character domain names too. Unfortunately for google g.gg is already registered (as, I suspect, will be the other 25 possibilities).
Shortest domain aren't necessaily the quickest or easiest to type.

Windows users can type in AND go to x.com in 3 key presses:

x
CNTL + ENTER
Technically, typing the same character twice is slower (unless you are scanning and pecking).

With fingers staggered, you should be able to type to different letters faster than the same one twice as you could press the second key at the instant the first key was released, without having to change any motion (ie transition from release (finger up) to press finger down)

Just my $0.02 :P
Since .cc is the same character it would make the domain the quickest to type as well as the shortest.
http://www.google.cn/webhp?source=g_cn
I think you'll find that http://dk./ is shorter. It used to work without the dot, but for some reason it doesn't any more
The gg cctld allows single character domain names too. Unfortunately for google g.gg is already registered (as, I suspect, will be the other 25 possibilities).
Shortest domain aren't necessaily the quickest or easiest to type.

Windows users can type in AND go to x.com in 3 key presses:

x
CNTL + ENTER
Surely the length of the letter i is shorter than g? I see i.gg is 'available'
Technically, typing the same character twice is slower (unless you are scanning and pecking).

With fingers staggered, you should be able to type to different letters faster than the same one twice as you could press the second key at the instant the first key was released, without having to change any motion (ie transition from release (finger up) to press finger down)

Just my $0.02 :P
g.gg would be pretty kool...although if I remember rightly, ain't that the name of a pr0n distributor from germany???