Best BiS Tooltip TBC shows BiS status for any gear directly in your tooltip.

When you hover over any gear piece it shows whether that item is BiS for your current spec, and for which raid phases. It's color-coded so you can instantly see the item's value at a glance.

Sources of Info & Why you can trust it:

Main source is Wowhead class guides
Cross-checks: Icy-Veins, Logs and Class Discords
Manual check for all the classes
In-house testing by our guild

Disclaimer:

BiS list - by its nature - can't account for:

Your raid comp (access to crucial buffs)
Fight lengths and individual bosses (your raid's dps)
Advanced theory-crafting (such as the arcane missiles build for mages)

Still it covers your best over-all options and it sure helps make desicions when you have 10 sec to roll on the item - but it can't think for you :)

Supported specs (TBC Classic 2.5.5)

All major PvE DPS, healing, and tanking specializations are covered, including:

Fire Mage, Arcane Mage, Frost Mage
Destruction Warlock, Affliction Warlock
Balance Druid, Resto Druid, Feral Druid (Dps and Tank)
Holy Paladin, Protection Paladin, Retribution Paladin
Protection Warrior, Fury Warrior, Arms Warrior
Shadow Priest, Holy Priest
Enhancement Shaman, Elemental Shaman, Resto Shaman
Survival Hunter, Beast Mastery Hunter
Combat Rogue

Phases supported

Pre-Raid, Phase 1, Phase 2 — each item is tagged for the phase it's BiS in, so the tooltip stays relevant throughout the progression. Upcomming phases will be supported.

Color coding

Orange— Absolute BiS
Purple — Close to BiS (usually 2nd / 3rd BiS)
Light blue — Sub-BiS / Optional / Viable alternative (Still good but not that good)
Light green — Further Options

I decided to refrain from strict numerical ranking because it creates a false sense of certainty when TBC has many variables (your raid comp and raid dps for example) and - more often than not - item #4 can be very close or better than #2. I think it's way more fair and not misleading while still providing the bulk of the info.

This addon also has useful suffixes such as, for example, "Absolute BiS - Mitigation" or "Close to BiS - Fire Destro"

No configuration needed. Install and go.