No, I'm not talking about Seal of Blood.
With the release of patch 3.0, Seal of the Crusader was removed because it was a DPS seal that was always going to be second to seals that added holy damage to attacks. However, it has become ever more apparent that the Seal that should have been retired is Seal of Justice.
In TBC, SoTC was impotent as a DPS seal because it was operating in an environment with only one on-demand attack (Crusader Strike).
See, the seal provided a heavy AP boost, a heavy haste boost, a decrease in auto-attack weapon damage, and an increase in Crusader Strike damage. (because it was not linked to the haste buff, it received no damage reduction, but did gain the extra attack power.
Things have changed since then, possibly most important is that all seals have judgments that deal damage. This was the major short-coming of SoTC; it didn't scale with it's Judgment debuff, and its Judgment dealt no damage on cast.
If the seal were still in existence today, this is what it would provide: a good DPS increase in auto-attack damage, a decrease in auto-attack burst, an increase in Crusader Strike damage, Divine Storm damage, Exorcism damage, Consecration damage, Righteous Vengeance damage, Judgment damage, HoW damage, and even healing.
What really strikes me about the list above is that it is an unbelievably more balanced combination of damage increases in a PvP setting than Seals like Blood and Righteousness were / are.
The major problems that have arisen in balancing Paladin burst in PvP have been caused by a system that deals burst damage by hitting enemies repeatedly with medium damage strikes that come simultaneously in clusters.
(Auto-attack + CS + SoB/SoR + SoB/SoR all at the exact same time)
This makes a Seal like Crusader the perfect 'tuning knob' (GC's new favorite PvP metaphor) for Retribution PvP damage.
It would organize Ret's damage dealing in paced, high-damage strikes, complimented by auto-attacks with lower burst but higher sustained damage.
All that would need to be done to make this Seal "the" PvP seal of choice would be to gut the Seal that should have been removed (Seal of Justice) and turn it into this:
Grants the Paladin AP equal to [600+.20*AP] and increases your melee attack speed by 40%, but each attack deals less damage. Unleashing this seal's energy will cause damage = to [1 + 0.25 * SPH + 0.16 * AP] / [(1 + 0.25 * SPH + 0.16 * AP)/Weapon speed]
and then add this to fanaticism:
While your Seal of Justice is active, your melee attacks increase your run-speed by 3/6/10% for 20 seconds. This effect does not stack with other movement speed increasing effects. Stacks up to 3 times.
Or even alternatively, a snare effect (although I personally prefer the +speed).
This would mean that Paladins in PvP would have the option to choose a Seal that better allows them to stay in melee range at the cost of their highest burst potential, as well as giving Ret a physical DPS seal for fights like Lady Deathwhisper's adds, and opening up new gearing possibilities with Armor Penetration (yes, I know it's going bye-bye, but 10 or so % armor penetration would be a very cool glyph for the seal).
[EDIT]: Forgot to mention two other good PvP attributes of this seal: It would mean less unresistable, un-mitigated by armor damage for a melee DPS spec, and it would mean Paladin PvP builds could be more viable without placing 5 points in holy.