SpellReplay is a TBC/WotLK AddOn that was originally made for Sbkzor in order to backport a retail addon widely used by streamers called TrufiGCD. The AddOn scrolls smoothly and speeds up when multiple spells are used at the same time, making it easier to highlight good plays.

It has been built from scratch to also include and display:

Missed spells

White hits

Spell rank

Spell damage/healing

Mana gains

Pet spells

Poisons applied (or resisted) on Shiv

… and much more.

The additions mentioned above are adjustable. You can also rescale the frame, change its scrolling direction, speed (ie. slower scrolling while casting), and modify the number of spells to display.

Settings are accessible from Interface > AddOns > SpellReplay or by simply right-clicking on the background square.