From Halopedia, the Halo wiki
A Halo fan since I read the first book back in 2002, long before I ever played Halo PC in 2003.
Saving Private Ryan, The Avengers (Marvel), Black Hawk Down, a lot more I can't remember. The Walking Dead, The Pacific, Band of Brothers, Red Dwarf, Top Gear. Linkin Park, Breaking Benjamin, Beethoven, Johnny Cash, Celldweller, Blue Stahli, and a lot of others... Anything by Harry Turtledove, most Tom Clancy, and the earliest Halo Books (anything by Nylund) Halo series, Empire Earth, Europa Universalis, Nexus: The Jupiter Incident, Crusader Kings 2, Half-Life series, anything by Tripwire. Pizza. More pizza. Root beer. MORE. ROOT. BEER. And Dr Pepper.
The reveal of the Gravemind, the Last Stand of Noble Six, the Battle for Delta Halo's Control Room, and all of Forward Unto Dawn
The "ending" of Halo 2, the first reveal of the Flood in Halo CE, seeing my carpet of Marines eaten by Flood in Halo Wars, and the deaths of Sergeant Johnson and Miranda Keyes. And Jacob Keyes. :(
If I had to place them in order... probably Halo CE, ODST, Halo 3, Halo 2, Reach, with Wars and 4 tied.