WalterEagle with some fabulous analysis:

I log how many lines each character has. A line is any uninterrupted dialogue until someone else talks or the scene or conversation changes; the number of times each person talks. I do it while I watch and it is not very time consuming beyond entering the number in Excel for 5 minutes to add them up after each season. Here are the results for the series to date.

1. Tyrion Lannister - 1002
2. Cersei Lannister - 530
3. Daenerys Targaryen - 507
4. Jon Snow - 489
5. Arya Stark - 441
6. Jaime Lannister - 437
7. Sansa Stark - 389
8. Theon Greyjoy - 359
9. Tywin Lannister - 355
10. Eddard Stark - 341

11. Robb Stark - 317
12. Petyr Baelish - 304
13. Samwell Tarly - 298
14. Catelyn Stark - 298
15. Jorah Mormont - 262
16. Bran Stark - 256
17. Joffrey Baratheon - 250
18. Varys - 241
19. Davos Seaworth - 234
20. Shae - 221

21. Sandor Clegane - 219
22. Brienne Tarth - 208
23. Bronn - 190
24. Stannis Baratheon - 179
25. Ygritte - 159
26. Margaery Tyrell -150
27. Oberyn Martell - 129
28. Melisandre - 126
29. Osha - 124
30. Gendry - 121

31. Robert Baratheon - 117
32. Missandei - 113
33. Grand Maester Pycelle - 111
34. Grenn - 110
35. Ramsay Snow - 109
36. Talisa Maeger - 104
37. Olenna Tyrell - 100
38. Gilly - 98
39. Jeor Mormont - 91
40. Maester Luwin - 87
40. Renly Baratheon - 87

42. Podrick Payne - 86
43. Alliser Thorne - 85
44. Ros - 84
45. Barristan Selmy - 82
46. Roose Bolton - 81
47. Jojen Reed - 79
48. Tormund Giantsbane - 76
48. Lysa Arryn - 76
50. Meera Reed - 73

51. Eddison Tollett - 70
51. Viserys Targaryen - 70
53. Thoros - 67
54. Locke - 66
55. Loras Tyrell - 63
55. Janos Slynt - 63
55. Yara Greyjoy - 63
58. Hot Pie - 59
59. Hodor - 57
60. Daario Naharis - 54

61. Lancel Lannister - 51
62. Khal Drogo - 46
63. Shireen Baratheon - 45
63. Mance Rayder - 45
65. Pypar - 43
66. Maester Aemon - 42
66. Kraznys mo Nakloz - 42
68. Jaqen H'ghar - 41
68. Salladhor Saan - 41
70. Beric Dondarrion - 40
70. Karl Tanner - 40

72. Doreah - 39
72. Qhorin Halfhand - 39
74. Yoren - 37
74. Xaro Xhoan Daxos - 37
74. Walder Frey - 37
77. Jory Cassel - 36
78. Septa Mordane - 35
78. Qyburn - 35
80. Spice King - 34

81. Rast - 33
81. Robin Arryn - 33
81. Rickard Karstark - 33
81. Selyse Baratheon - 33
85. Tommen Baratheon - 32
85. Rodrik Cassel - 32
85. Alton Lannister - 32
88. Grey Worm - 31
88. Anguy - 31
88. Orell - 31

91. Irri - 30
91. Craster - 30
91. Mirri Maz Duur - 30
94. Syrio Forrel - 29
95. Rakharo - 28
95. Edmure Tully - 28
97. Gregor Clegane - 27
97. Matthos Seaworth - 27
99. Balon Greyjoy - 26
100. Benjen Stark - 25

SEASONAL TOP 10s

SEASON 1

1. Eddard Stark - 341
2. Tyrion Lannister - 222
3. Catelyn Stark - 159
4. Daenerys Targaryen - 151
5. Jon Snow - 149
6. Robert Baratheon - 117
7. Cersei Baratheon - 115
8. Petyr Baelish - 115
9. Jorah Mormont - 104
10. Arya Stark - 102
10. Robb Stark - 102

SEASON 2

1. Tyrion Lannister - 330
2. Theon Greyjoy - 171
3. Cersei Lannister - 159
4. Arya Stark - 129
5. Daenerys Targaryen - 125
6. Robb Stark - 123
7. Catelyn Stark - 93
8. Jon Snow - 90
9. Davos Seaworth - 89
10. Stannis Baratheon - 88

SEASON 3

1. Tyrion Lannister - 224
2. Jaime Lannister - 120
3. Daenerys Targaryen - 106
4. Arya Stark - 105
5. Tywin Lannister - 99
6. Sansa Stark - 97
6. Cersei Lannister - 97
8. Davos Seaworth - 96
9. Robb Stark - 92
10. Jon Snow - 89

SEASON 4

1. Tyrion Lannister - 225
2. Jaime Lannister - 172
3. Jon Snow - 161
4. Cersei Lannister - 159
5. Tywin Lannister - 151
6. Oberyn Martell - 129
7. Daenerys Targaryen - 125
8. Sandor Clegane - 120
9. Samwell Tarly - 115
10. Arya Stark - 105

TRIVIA

1. HOW IS NED SO HIGH? Well, many reasons. A) There were far fewer characters total in Season 1, so on average the main characters got a lot more focus (twelve people had at least 100 lines, while in Season 3 only four people did); B) Ned was a real lead who never missed episodes, whereas most other characters frequently miss multiple every season (Davos was in three seasons but only four more episodes than Ned); C) Ned averaged a whopping 34 lines per episode, whereas most main characters average 8-15ish...if you do the math, it takes awhile for them to catch that (he got 77 in one episode once, and more than at least 40 in four other episodes, which is very rare for people who aren't Tyrion); D) Ned had a major storyline in pretty much all his episodes (often 10+ scenes), while some major characters like Bran, Littlefinger, Varys, Theon, and sometimes even Jon and Robb often just get only one scene in a number of episodes, which takes awhile to accumulate; E) his high ranking isn't that crazy because you can tell a bunch more people will surpass him during Season 5.

2. Most lines in an episode: Ned, with 77 in "The Wolf and the Lion".

3. Runner-up: Samwell Tarly with 71 in "The Watchers on the Wall". Sam's total in this episode was higher than his total for Season 1, Season 2, or Season 3.

4. Most times 1st place in an episode: Tyrion (12) followed by Ned (6).

5. Most times 2nd place in an episode: Tyrion (8) followed by Jon (4).

6. Most times 3rd place in an episode: Jon (5) followed by Arya (4).

7. In Season 4, a Lannister came first place in each of the first seven episodes. *Highest lines-per-episode average: Ned (34.1), followed by Tyrion (27.8), Oberyn (18.4), Davos (16.7), Robert (16.7), and Jaime (15.6).

8. Most lines by a one-episode character: Mero (17 in "Second Sons").

9. Most lines by a guest star: Oberyn (127).

10. Fewest lines by a credited regular: Khal Drogo (46).

11. Least prominent character to get 1st place in an episode: Viserys Targaryen (25 lines in "A Golden Crown").

12. Tyrion and Cersei have been in the most episodes (36), followed by Arya (33), Daenerys (33), Jon (32), Sansa (31), and Jorah (31).

13. Tyrion has the most lines in season premieres (126) and season finales (80).

14. Only Tyrion makes the top 5 for every season. Arya, Jon, Daenerys, and Cersei make the top 10 for every season.

15. The most prominent characters who never got first place in an episode are Jon, Arya, Sansa, Littlefinger, Catelyn, Jorah, and Joffrey.

16. The most prominent character who never made the top 10 for any season is Bran, followed by Joffrey and Varys.

If you want the data for any episode, or any other number-crunching, I have that information too.

One thing is clear: the writers are VERY efficient at telling a story with 100+ characters.

Also, if you look at the ranking for all seasons, you see the relative importance of the characters to the overall show / story. Fascinating.

From zephyrtr:

Interesting tidbit: there have been 84 total deaths on the show so far (only including named speaking roles, with a couple exceptions).

• Season 4 was the most bloody season, with 24 fatalities — which might suggest the low amount of survivable maimings and dismemberments this season.
• Rains of Castamere (the Red Wedding) is still the bloodiest episode with 7 deaths, but Season 4 came close with two back-to-back episodes with 5 deaths each.
• There has been the death of at least 1 king every season.
• Since the start of the show, the only original Lords Protector still alive are Oberyn Martell's brother Doran and Margaery Tyrell's father Mace.

Actually, on that last part:

Lord Protector is a title that refers to a male noble who married a female ruler of a castle or territory, like Petyr Baelish being Lord Protector of the Vale. What I think you mean is the Lords Paramount of the realm.

Point of view chapters in the first three books:

        I	II	III	Total
Bran	7	7	4	18
Catelyn	11	7	7	25
Daenerys10	5	6	21
Eddard	15	0	0	15
Jon	9	8	12	29
Arya	5	10	13	28
Tyrion	9	15	11	35
Sansa	6	8	7	21
Davos	0	3	6	9
Theon	0	6	0	6
Jaime	0	0	9	9
Samwell	0	0	5	5

Super - thank you.

Happily! Does not include books 4 and 5 because spoilers.

"I wonder if the actor playing Hodor had trouble memorizing his 57 lines."

Reddit comments:

http://reddit.com/r/gameofthrones/comments/28cikf/s4e10_characters_with_the_most_lines_in_game_of/ci9mo8m

Another chart from the data from mab6bf:

Click through to see the big version.

More data on season 4:

Tyrion Lannister - 225
Jaime Lannister - 172
Jon Snow - 161
Cersei Lannister - 159
Tywin Lannister - 151
Oberyn Martell - 129
Daenerys Targaryen - 125
Sandor Clegane - 120
Samwell Tarly - 115
Arya Stark - 105

Sansa Lannister - 104
Brienne Tarth - 99
Petyr Baelish - 71
Podrick Payne - 64
Alliser Thorne - 62
Ramsay Snow - 60
Jorah Mormont - 55
Bronn - 55
Missandei - 53
Margaery Tyrell - 52

Grenn - 49
Davos Seaworth - 49
Bran Stark - 49
Shae - 49
Reek - 44
Lysa Arryn - 43
Tormund Giantsbane - 41
Gilly - 40
Meera Reed - 40
Varys - 36

Joffrey Baratheon - 35
Eddison Tollett - 34
Stannis Baratheon - 33
Hodor - 32
Karl Tanner - 32
Grand Maester Pycelle - 30
Olenna Tyrell - 29
Locke - 28
Melisandre - 27
Grey Worm - 26

Tommen Baratheon - 26
Janos Slynt - 25
Ygritte - 25
Jojen Reed - 25
Roose Bolton - 25
Selyse Baratheon - 24
Pypar - 23
Daario Naharis - 23
Ellaria Sand - 23
Barristan Selmy - 22
Robin Arryn - 22

Trivia:

1. Jaime and Cersei were in the most episodes (9).

2. Of the regular cast members, Joffrey, Melisandre, Ramsay, and Theon were in the fewest episodes (3), a record low for regulars in any season.

3. Sam had the most lines in an episode, with 71 in "The Watchers on the Wall". It is also the second-most lines anyone ever had in an episode with the exception of Ned's 77 in "The Wolf and The Lion". That one episode alone is also a higher total than Sam's total lines in any other season.

4. A Lannister had the most lines in each of the first seven episodes.

5. Here are the halfway point results for comparison.

A few comments:

http://reddit.com/r/gameofthrones/comments/28cdu5/s4e10characters_with_the_most_lines_in_season_4/

Deaths by episode, weighted by number of lines:

100+ Reddit comments:

http://reddit.com/r/gameofthrones/comments/28gvmt/all_show_deaths_by_episode_weighed_by_number_of/

Holding out for Syrio Forrel!

I'm holding out for Syrio Forel, Jaqen D'Ghar, Gendry, Rickon, Osha, and the Hound!