If you fly a helicopter in front of Los Santos City Hall and look south, the eye from the Penris Building's logo aligns exactly with the top of City Hall's pyramid — recreating the All-Seeing Eye / Illuminati symbol.
Source: Penris Building — CC BY-SA
The Penris Building's creepy eye logo — line it up with City Hall's pyramid from the right angle and bam, you've got yourself a full-blown Illuminati symbol.
The 'Ghost Car' in the woods? It's the exact car from Leatherface's movie finale.
GTA: San Andreas
A lone mountain bike in the woods sparked a decade-long GTA mystery about a silent killer.
GTA: San Andreas
The most haunted county in GTA San Andreas has a beach where literally no one ever spawns.
GTA: San Andreas
You can trick Ballas into giving Grove Street to the Aztecas — without ever fighting them yourself.
GTA: San Andreas