Integrations
There are various ways to make inserting emojis easier.
OSX
You can pull up the emoji keyboard by hitting ctrl+⌘+space
Windows 10
You can pull up the emoji keyboard by hitting Win+.
Ubuntu 20
You can press Super to search for the emoji name, but only the first 5 matches are displayed. This works for "book", but not for "bug".

Ubuntu (all versions)
Launch the "Characters" application.

Gnome Shell
You can show a list of emoji to copy to your system clipboard using the Emoji Selector Gnome extension. This extension recognises commit message emoji labels like 'refactor', 'version', 'wip'.
Atom Editor
Install package for autocomplete-emojis. In the package settings, check the box for "Enable Unicode Emojis".
Atom can also help with using emoji in commit message by installing git-plus
Sublime Text
Install package for GithubEmoji.
Vim
Install package for Vim-emoji.
Add set completefunc=emoji#complete to .vimrc and then run emoji completion with CTRL-X CTRL-U
npm
Create an .npmrc file and set the message value.
message = "🔖 %s"
Emacs
Install emoji-cheat-sheet-plus.
Bring up the emoji buffer with:
M-x emoji-cheat-sheet-plus-insert