Let's make this a running list!

1. They take chances with their characters: A female director of NCIS, a Goth forensic scientist, an Israeli agent... need I continue?
2. They have a farting Hippo!
3. Ducky's personality.
4. Gibbs does have a soft spot.
5. McGee can hack anyone, anywhere!
6. Ziva's way with English idioms.
7. Gibbs' unconventional approach to investigating.
8. Abby!
9. The cars!
10. They always get their man... or woman.
11. The way Tony always seems to say the wrong thing....
12. How they all care for each other and the strange ways they show it.
13. Gibbs' pride in his team.
14. Gibbs' name: Leroy Jethro Gibbs.
15. Jenny's house!
16. The fact that they really have a genuine Mass Spectrometer.
17. Ziva's killing skills trained as a Mossad officer!
18. The way Ziva handles interrogations.
19. The way Gibbs handles interrogations.
20. Gibbs never getting tired of drinking coffee!
21. Characters can actually get hurt (Shot, etc.) and die (I may not always like it, but it keeps life interesting.)
22. Gibbs' driving.
23. Ziva's driving.
24. Tony's 1001+ nicknames for McGee.
25. Gibbs' way with kids.
26. Jen's way with kids.
27. Abby and McGee playing MMORPG's.
28. MorphPro software (I can't wait for Abby to catch someone messing with it!)
29. Gibbs' "Pleeeez...."
30. The way they are so close to each other.
31. The way Gibbs remembers all of his rules (I wonder how long it took for him to remember them all).
32. How Ziva is able to waste time to learn 18 different ways to kill people with a paper clip
33. Ducky's mother
34. McGee
35. Tony's knowledge of movies
36. The secret romance between Jimmy and Agent Lee
37. The way they put their agents in danger (ie Tony hanging off a wall in Leap of Faith)
38. They work all hours god gives to solve a case
39. Tony's whinging and whining
40. Ziva plaiting her legs when she finally gets out of the container she and Tony were held in
41. The banter among the team
42. They never go on strike
43. Gibbs' hair never gets mussed
44. Neither does Abby's
45. Jen's ability to walk fast in impossible stiletto heels
46. Ducky always knows how the victim died however difficult it is to find out
47. Gibbs' head slapping.
48. The 'loving' relationship between Tony and McGee
49. The way Abby always cares for the team and whatever animals come her way.
50. Tiva
51. The humor
52. Tony and Ziva's dysfunctional caring of each other no matter how subtle
53. The way Gibbs appears seemingly out of nowhere, when you least expect it.
54. The professional competition between the team when giving info to Gibbs.
55. The way Abby is always trying new methods of predicting the exact moment Gibbs enters her lab.
56. The way the cast gells with each other.
57. The idea of using a lift as a 'conference room'
58. Gibbs' gut is never questioned
59. Gibbs' gut gets better results than the Oracle of Delphi, etc., - maybe it could give us the winning numbers on the lottery?
60. Gibbs being the "father" figure of the team.
61. Gibbs "talking" to his team with his '"stares".
62. Gibbs never gets a speeding ticket despite going over the limit and not using the siren
63. Gibbs' liking of "eyeballing" people.
64. Gibbs' liking of invading one's personal space to throw you off balance.
65. The way Gibbs creeps up on people to catch them out
66. I can't choose just one, everything is the best!
67: Abby's music
68: Tony DiNozzo
69: Tony's movie quotes :)
70. The way Gibbs' 1000 watt smile just appears out of nowhere
71. The dialogues
72. The banter
73. Drama interlaced with humour, or
74. Humour interlaced with drama
75. How Tony's always getting smacked.
76. Abby's Addiction To Caf-Pow Drinks
77. The Cute Little Gabby Scenes
78. Abby Investigating Who Stole Her Cupcake!!
79. Gibbs' boat and basement
80. I love everything but mostly Gibbs in the shower if I had to choose
81. Abby's (and sometimes Gibbs') signing
82. Ziva!
83. The way they are one big family!
84. Humour interlaced with drama AND romance!
85. McAbby!!!!!!!
86. McGee's geekiness!!!
87. The intrigue, especially with other agencies, CIA & FBI, and the international setup.
88. Gibbs cuffing the team members round the head
89. The light heartiness of the show, relationships and the BEST random quotes and TIVA
90. Abby's cute gothic outfits!!!!!!
91. Gibbs'complete lack of computer and technological intellect and being confused by Abby or McGee
92. The fact that Tony and Jimmy are apparently secret friends.
93. The way that Abby teases Gibbs but hardly gets into trouble for it but I love the whole thing
94. Ducky's ramblings of random stuff from his youth
95. Gibbs walking out on Ducky's ramblings of stuff from his youth
96. Kate's bat drawing of Abby
97. The hatred between Tony and Trent Kort of the CIA
98. Tony's undercover assignment in season 4 to catch La Grenouille
99. Ziva's terrible driving skills
100. Tony's car getting stolen and then being seen on a high speed chase on national television, then becoming a total write-off, while the thief survives unharmed.
101. TIVA, McAbby, Gabby, etc. Gotta love them!!!!
102. Zividioms and the wit/humour!♥
103. The way Abby talks to her machines, calls them her babies, and even challenges the Mass Spec to a duel.
104. Ducky talking to dead people as he autopsies them.
105. Gibbs " Man up marine"
106. When Abby and PalmerPalmer(Mostly Palmer) discover something while Gibbs is in the room, Abby gets a kiss on the head, and Palmer gets a Gibbslap on the head.
107. Probie Sandwhich
108. The random funny quotes