Origin

Creed's Tactical Genius is a meme that revolves around a special rule of one Imperial Guard character from Warhammer 40,000, Lord Castellan Usarkar E. Creed, that allows him to give any unit the Scouts rules. This rule allows units to either A) get a head-start on their movement (moving before anybody else moves, even allowing two movements if you get to move first) or B) use the Outflank special rule.

About

The Outflank Special Rule allows units to attack an enemy by coming in from the left or right side of the board, determined by a dice roll. Because Tactical Genius can be used on any unit, this Outflank rule can be applied to any unit, even ones that you should've seen coming a mile away, such as Baneblade (A tank the size of a building), or Titans (giant robots. Typically these are Warhound Titans, which are about a foot or two in height [relative to basic infantry, which are no more than an inch, this makes them several hundred feet tall]). The capability for Baneblade and Titans to use this rule is what lead to this meme, especially considering that this rule is never properly explained. Even worse is that it's entirely possible to do this to multiple such units, provided they're within the same relative unit (IE a squadron).

As such, 4chan took Creed's Tactical Genius and ran with it, abusing it to degrees that are just plain silly, such as Baneblades coming out from behind telephone poles, or Titans out of swimming pools. However, given that the Scouts special rule was designed for actual scouts, as in infantry or motorbikes, this is entirely feasible, just downright silly. Strangely, Tactical Genius cannot be used on cavalry (Such as Rough Riders), perhaps because Creed's army isn't supposed to be fielding those guys.

Usage

A typical example of the meme is as follows:

"So I'm sitting there on my computer when I hear some rumbling. Thinking it was my chair I stood up and looked at it, not finding anything unusual. I sat down, then looked back and saw myself staring face-to-face with a Baneblade. I have no idea how that got there, it must've taken some sort of tactical genius to…CREEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEED!" (the meme always ends with screaming Creed's name)

There are of course variations, but they are always revolving around something physically impossible happening, something that can only be attributed to Creed's Tactical Genius.

1d4chan has an entry on Creed, located here: http://1d4chan.org/wiki/Creed

In the entry, they have a few examples (in the "writefaggotry" section), as well as a slightly more detailed explanation behind how the meme works in an example.