Erick Hitter

WordPress 3.0 introduced a native shortlinks feature, which builds URLs using query strings. This plugin converts those URLs to ones using pretty permalinks, which makes for a nicer-looking URL and improves shortlinks’ ability to be cached.
Posts and pages are supported by default, while filters make it possible to support other post types.
For example, https://example.com/?p=123 becomes https://example.com/p/123/.

ETH Simple Shortlinks

Convert WordPress's query-based shortlinks to pretty permalinks that are cacheable. https://example.com/?p=123 becomes https://example.com/p/123/.

edwardrpool

This plugin is ultra lightweight. It adds a media button above the tinyMCE editor on both the page and post editor, which when pressed copies a shortlink to your clipboard.
The idea behind this plugin is to add short-linking capabilities, without all the bloated code found in other plugins. This plugin does not alter the database, nor is any data saved or collected. It uses the built in WordPresspost/page ID’s in the URL.

ERP ShortLinks

A very lightweight plugin which adds a shortlink button to the post/page editor for quickly sharing on social platforms.

ETH Simple Shortlinks vs ERP ShortLinks