Gargron

This widget shows all tags that are anime titles as a dropdown menu. It creates a taxonomy called Anime, you only need to tag your posts not in the ‘Post Tags’ box, but the ‘Anime’ box.

Anime Dropdown Widget

This widget shows all tags that are anime titles as a dropdown menu. Using WordPress' custom taxonomies.

beeender

This is a similar plugin with WP-Cumulus (https://wordpress.org/extend/plugins/wp-cumulus/) but implemented with HTML5.
This plugin requires the modern browsers which support HTML5.

Cumulonimbus

Cumulonimbus allows you to display your site's tags on the surface of a rotating sphere.

Anime Dropdown Widget vs Cumulonimbus