The Major Sins

1. Associating Anything with Allah (SWT)
2. Murder
3. Practising Magic
4. Not Praying
5. Not Paying Zakat
6. Not fasting on a Day of Ramadan without excuse
7. Not performing Hajj, while being able to do so
8. Disrespect to Parents
9. Abandoning Relatives
10. Fornication and Adultery
11. Homosexuality
12. Interest
13. Wrongfully consuming the Property of an Orphan
14. Lying About Allah (SWT) and his Messenger (SAW)
15. Running away from the battlefield
16. A leader's deceiving their people and being unjust to them
17. Pride and arrogance
18. Bearing false witness
19. Drinking alcohol
20. Gambling
21. Slandering Chaste Women
22. Stealing from the spoils of war
23. Stealing
24. Highway robbery
25. Taking false oath
26. Oppression
27. Illegal gain
28. consuming wealth acquired unlawfully
29. committing suicide
30. frequent lying
31. judging unjustly
32. giving and accepting bribes
33. imitating the opposite gender
34. being cuckold
35. marrying a divorced woman in order to make her lawful for the first husband
36. not protecting oneself from urine
37. showing off
38. learning knowledge of the religion for the sake of this world and concealing that knowledge
39. betrayal of trust
40. recounting favors
41. denying Allah (SWT)'s decree
42. eavesdropping
43. carrying tales
44. cursing
45. breaking contracts
46. believing in fortune tellers and astrologers
47. a woman's bad conduct towards her husband
48. making statues and pictures
49. lamenting, wailing, tearing clothing and such when an affliction befalls you
50. treating others unjustly
51. overbearing conduct toward the wife, the servant, the weak, and animals
52. offending one's neighbour
53. offending and abusing Muslims
54. offending people and having an arrogant attitude toward them
55. trailing one's garment in pride
56. men's wearing of silk and gold
57. a slave's running away from his master
58. slaughtering an animal in the name of someone or something other than Allah (SWT)
59. to knowingly claim someone who isn't your father, as your father. 
60. arguing and disputing violently
61. hoarding water
62. giving short weight or measure
63. feeling secure from Allah (SWT)'s plan
64. offending Allah (SWT)'s righteous friends
65. not praying in congregation without an excuse
66. persistently missing friday prayers without an excuse
67. usuping the rights of the heir through bequests
68. deceiving and plotting evil
69. spying for the enemy of the Muslims
70. cursing or insulting any of the Companions of Allah (SWT)'s Messenger

What Obedience to Parents Actually Entails

An excerpt from the book "The Major Sins" by Muhammad bin 'Uthman Adh-Dhahabi:

K'ab al-Ahbar was asked about the meaning of "disrespect to parents," to which he replied: " If the father or mother assigns him a task, he does not do it; if they order him to do something, he does not obey them; if they ask him for something, he does not give it to them; and if they entrust him with a thing, he cheats them in it."