Here is a curated list of the best UI addons for version 3.3.5, categorized by function.

Non-negotiable for raiding. It provides timers for boss abilities, warnings for when to run out of the fire, and phase change alerts.

: Replaces the standard minimap with various "ubersexah" skins, such as rotating runes or minimalist squares. Combat & Raiding Essentials

This puts cooldown numbers directly on your action buttons. It sounds simple, but the default WoW UI just shows a sweeping shadow. OmniCC lets you know exactly when your defensive CDs are ready.

interface requires specific legacy versions of addons to ensure compatibility. Since modern versions of these tools won't work on the 3.3.5 client, you must source them from archives like the WoW 3.3.5 Addons Compendium or community forums.