That other wiki is another name for Gearspedia, the Gears of War canon wiki. The phrase "that other wiki" is used to avoid confusion such as:
Alice: Hey, I was on the Gears Wiki last night and found a really cool fanfiction! It's totally awesome!
Bob: What are you talking about? There's no fanfiction on the Gears Wiki!
Alice: Uh, yes, there is.
Bob: Uh, no, there's not.
Gearspedia is dedicated to the accumulation of canonical Gears of War information and is committed to accuracy and ease-of-use. There are a handful of devoted editors and admins who work to make the site a resource for their fellow Gearheads. Notability is encouraged, as well as good grammar and spelling.
Fanon gets deleted from Gearspedia. Why? Because this is the Gears Fanon Wiki, where fanon should be posted. Gearspedia is strictly for proven, canon information. Likewise, rather than creating canon articles here, direct links to the appropriate page on Gearspedia.
"That other wiki" to refer to Gearspedia was coined by Screennameless when she joined the Gears Fanon Wiki. She kept getting confused about which Gears Wiki she was referring to at any given time. Finally she got the idea of "that other wiki" from TVTropes.org, where Wikipedia is referred to as "that other wiki", partially as a joke and partially to avoid confusion.