One sample z-test to compare the
mean of a variable with some given number. This test is
applicable only if you know (or have a very good
approximation for) the standard deviation of
your variable. (Requires Gaussianity assumption.)
One sample t-test. Similar to
above, except that you do not need to know the standard deviation. (Requires Gaussianity assumption.)
Paired t-test for comparing the
means of two variables. (Requires Gaussianity assumption.)