Nanami and Yuzuru wind up being a lot happier as vampires. The fact that Yuzuru's human life sucked justifies this on his part, and from what we (don't) see of Nanami's home life she had more than a bit of the Parental Abandonment thing going as well.
Seiji Hama as well. When Mina comments that the lifestyle of a captive suits him, he mentions offhandedly that it's better than some other places he's been held that regularly subjected him to torture.
Crazy Awesome: The Earth Clan Elders. If their outrageous stories are to be believed (and it's implied by a few characters that they are), they wouldn't have been able to pull any of their stunts if they weren't batshit insane. For instance, only these guys would consider killing a shark that ate them by eating it from the inside out.
Ear Worm: The Opening Theme, Aiko Nakano's "Friends". And the Ending Theme as well, Hibiku's "Tsumeato" — for some even more than the Opening.
Fetish Retardant: Mina's constant nudity can get pretty annoying instead of arousing.
How some werewolves are born. Only male children can be werewolves but even then there's only a thirty percent of the child being a werewolf. The only way to be absolutely certain of getting a werewolf is to have sex... with the man in werewolf form. As of the final chapters of the manga, there may be an exception to the rule as the female werewolves are making a comeback in the form of Sanin's older sister Tatiana.
That shapeshifting weapon had Akira on the ropes, running him ragged and keeping him guessing on whose friend or foe. Then managing to mortally wound him when it cornered him. All seems lost, right? Fortunately for Akira, the weapon tries to be sadistic and transforms into Mina to add insult to injury. This however has the effect of making Akira very angry that it would mock his love for her. He gains the strength to go wolf and bite the thing's head clean off.
The students who barricade themselves in a chapel only to open the door when someone they are largely convinced had been kidnapped several days ago by the vampires they were hiding fromasks to be let in. This is after Akira told them that vampires would play such tricks and Yuki reminding them when they were about to do it.
Sanin. First he was betrayed, brain-damaged, and nearly killed by the werewolf who was supposed to be his partner for life during their trial in Siberia with Akira and Angie. Then his half-dead body was found by Telomere, who forcibly injected him with chemicals designed to make him a psychotic killer. Then, Angie manages to get through to him and restore what little humanity he has left after, you know, the brain damage and chemicals... and a Manchurian Agent injects him with berserker serum again, forcing a traumatized Akira to put him down in self-defense. And of course, he's shown in flashbacks to generally be the nicest guy you could ever hope to meet. And to just twist the knife deeper, in a last remaining shreds of his sanity, puts Akira's gun under his own chin for him to do it. His final tear-filled words before Akira pulls the trigger? "I... I'm sorry... A-Akira...".
Akira himself. How about having to kill your friend when you were just a kid, then have to live with the feeling you're an animal, just to find out out that another friend who was presumed dead, shows up, and then you have to kill him.