Apple - How do I get the Unicode code of a character from the Character Viewer?

In Character Viewer, click the gear icon in the top-left, then select "Customize List".

In the dialog that appears, scroll to the bottom and check "Unicode" under the "Code Tables" branch.

You should see something like this if you click on the "Unicode" item that's now in the left-hand pane (with unicode hex values down the left-hand column):

Alternatively, you can also right-click the character and select "Copy Character Info".

Then, if you paste into a text editor you get:

A
LATIN CAPITAL LETTER A
Unicode: U+0041, UTF-8: 41