Two-Player Games: Nim
To play, take turns removing pennies.
You can take as many pennies as
you'd like, but they can only be from
one row.
So during your turn, you could take
one or two from the first row, or you
could take one, two, or three from the
second, or one, two, three, or four
from the third row.
The person who is left with the last
penny loses!
SOURCE: http://pbskids.org/zoom/activities/games/