[Reach]

Yeah, there are tons of easter eggs.

A list of cool ones ones I've found:

Psychedelic hallway with pillars, trees and weird things on the ground in B

Guy laughing and throwing money around at the end of a creepy hallway in C

Developer Gallery with cool pictures in C

Underwater cave with a weird creepy tiki in it

Shaking room

Jet pack - and subsequent cliffside puzzle with a frozen guy inside