What's your favourite Call of Duty?

Everything before Ghosts I have very fond memories with friends and family. I'm maxed out level on all of them online (PSN).

Call of Duty: I was really into WWII shooters at the time, this one actually felt like a movie to me during those days.
Call of Duty 2: My first lick of CoD multiplayer - and it was on LAN. This is where I found a passion for FPS games. I liked them a lot already beforehand, but I just felt so competitive here with friends and family.
Call of Duty 3: Tanks were fucking hilarious.
Call of Duty 4: I can't imagine how many hours I've spent on this game. The oldschool mode glitches, the pubstomping with friends for the first time, unlocking the P90 for the first time, it was simply magical. Huge amounts of split screen time at parties in this game. The campaign is also one to go down in history. Internet down? Play campaign. Bored? Play campaign. See a singleplayer glitch someone did online? Try it out in campaign.
Call of Duty WaW: I wasn't too into the multiplayer in this game. I kept playing CoD4, but damn did this game have one hell of a campaign. I loved every inch of it, except veteran. Fuck those grenades. But co-op brings me back. There was a glitch to get an entire Ground War lobby into a co-op campaign session. It was great fun. What REALLY took most of my time with this game was the zombies mode. Ho. Ly. Shit. It was fantastic. Coming up with strategies, or just staying up late night with family and friends. I could not get enough of it.
Call of Duty MW2: A fitting sequel to such a deserving game. Even to this day I still play the game just because of how fun it is. The campaign was even more action and even more fun. The campaign took the story into a fascinating direction. No Russian will forever be burned into my mind. There was more depth to stealth. There was more bang to the explosions. The spec ops missions were another thing I sunk a lot of my time into. Looking back, it was the same deal with spec ops as I did with zombies. Come up with strats, stay up all night with friends or family, and just watch the juggernauts fall as we do cheap trick to cheap trick. However, the thing that was most memorable was the multiplayer. It was so good, even split screen at parties was addicting. When I think of the length and lifespan of a Call of Duty game's multiplayer (having the most players out of all of the games actively), I think of MW2. There was just so many crazy things. It felt so fast paced and made my heart rush so much.
Call of Duty Black Ops: Another wonderful game. The addition of bots made local multiplayer something fun for everyone at parties. The multiplayer online was very stiff and competitive, but also chill and relaxed too. Theater mode was the beginning of bragging rights between me and my friends. The campaign was a bit mind blowing. The story was full of twists and turns, and you actually felt like you were being fucked with. The zombies was taken to a whole new level. It was the thing I stayed up for countless nights with friends.
Call of Duty MW3: A nice bow to wrap the story up in the campaign. Wasn't my favorite, but I sure do have fond memories of it. Spec ops wasn't as a big deal as MW2, but I do remember staying up long nights playing survival mode. No, where this game really shined was the multiplayer. This was the beginning of me becoming a "tryhard" in video games. It wasn't to compete with anyone, it never was and it never will be. It's about bettering myself as a human being. Improving my thinking skills, acting under pressure, teamwork skills, hand-eye coordination, oh and not to mention the Mountain Dew and Doritos for that dank double XP. I loved the Face-off playlist, namely 3v3s. I had strategies and I ran them hard with my team. I absolutely treasured this game, not for it being competitive for me, but because it was actually fun. RSASS ACOG Silenced w/ RPG. Oh yeah, baby. Not only did I try hard, I was a fucking goofball.
Call of Duty BO2: Story was meh. Kinda sucked. Zombies was simply incredible this time around (except Tranzit, what the fuck were they thinking?). In this game, my competitive side completely took over. Within 3 months I maxed out my level and brought a lot of my efforts into the league matches. I followed the pro gaming scene here. I studied close, practiced aim, did everything I could to become the absolute best I possibly could. I knew (and still know) every map like the back of my hand and most of the callouts. I was the kind of person to challenge myself, no perks and no attachments in pubs. I'd still stomp. What I have really good memories of is the emblem editor. I really got to express my creative side here ^^

CoD4 is where the quickscoping boom happened, jsyk xP
Also, I recall there being the most map glitches in that game more than any other Call of Duty. Other than that, the game was pristine.