At the beginning of Black Ops 2, Mason is living in Alaska with his son David, when Hudson and Oliver North come to ask for his help in rescuing Frank Woods. Mason doesn't want to leave David, but he knows what he has to do.
Mason: "It's Uncle Woods, son. I have to help him. He'd do the same for me. We'rebrothers."
The ending of the mission "Old Wounds" has Mason, Woods, and Hudson left out to rot in the desert. Who should come to rescue them? "Tricky Vic." Reznov returns and saves Mason and his friends. The tone of voice David Mason uses implies that Mason Sr. spoke very fondly of Reznov to his son and honestly believed that his friend had returned just to save him. Woods lampshades the absurdity of it actually being Reznov by reasoning that the real Reznov would have stuck around and explained how he survived. But hey, he's "Tricky Vic" for a reason right?
If Woods shoots Mason in the legs rather than the head in "Suffer With Me", Mason is later revealed to still be alive, and he finally reunites with son after almost thirty years.
It gets even better, considering Woods and Mason, both pushing 90 years, start bantering like they did when they were still soldiers.
Hudson's demise. Despite being forced to betray his friends to the whims of a psychotic drug lord, he was willing to sacrifice his own life and die a horrible death to keep his friend's son alive.
Also, we see a flashback to David seeing Alex's body and beggining to break down crying. After that, we zoom in close to Alex's face, and see it twitch. The implication? Alex began to wake up because of David; If it wasn't for his son, he would have died.The Power of Love indeed.
David and Woods in the veteran's cemetery.
Woods: (nodding at Mason's grave) He's happy to hear that.
David: You talk to the dead now, Sarge?
Woods: Nah. They talk to me.
Karma/Chloe calling out Menendez on Jimmy Kimmel Live! in the ending, if both are still alive. Seeing Menendez break the TV in his cell by headbutting it is so satisfying, considering his plan effectively leads to none of the ends he hoped to reach. Cordis Die members didn't riot after his death considering he's still alive, his celerium virus is removed without causing too much irreparable damage, and he spends the rest of his life in a cell.
The post-credits scene in a way. Yes it's absurd, and yes, everyone is OOC, but they're also friends and attenting a Avenged Sevenfold concert. Woods even reassure Menendez that he can handle playing in front of a crowd.