TL;DR

If you want to show the name of the latest tag, use:

git for-each-ref --sort=-taggerdate --count=1 --format '%(tag)' refs/tags

Some background

The command git for-each-ref is pretty useful if you want to find something in a number of commits (or tags in this case). It allows you to use variations of output and sorting methods. For example:

Show all tags including the message

git for-each-ref --format '%(refname) %(contents:subject)' refs/tags

(this is btw. very similar to git tag -n1)

Show all tags sorted by date, oldest first

git for-each-ref --sort=taggerdate --format '%(refname)' refs/tags

Show all tags sorted by date, newest first

git for-each-ref --sort=-taggerdate --format '%(refname)' refs/tags

Show latest two tags

git for-each-ref --count=2 --sort=-taggerdate --format '%(refname)' refs/tags

Show latest tag with its non-ambiguous short name

git for-each-ref --sort=-taggerdate --count=1 --format '%(refname:short)' refs/tags

Show latest tag

git for-each-ref --count=1 --sort=-taggerdate --format '%(tag)' refs/tags 

(note: this is the same as the previous one, but uses the tag field)