All Minecraft target selector arguments

Solution 1:

Via the Minecraft Wiki

Present in 1.8

1. x = X coordinate of search origin
2. y = Y coordinate of search origin
3. z = Z coordinate of search origin
4. r = radius maximum in blocks
5. rm = radius minimum in blocks
6. m = gamemode (0: survival, 1: creative, 2: adventure, 3: spectator)
7. score_[name] = score maximum
8. score_[name]_min = score minimum
9. c = maximum targets (not minimum, of which there is none)
10. l = level maximum
11. lm = level minimum
12. team = scoreboard team name
13. name = player username or entity CustomName (translated default name if no CustomName)
14. dx = number of blocks in the X direction to search in
15. dy = number of blocks in the Y direction to search in
16. dz = number of blocks in the Z direction to search in
17. rx = vertical rotation maximum
18. rxm = vertical rotation minimum
19. ry = horizontal rotation maximum
20. rym = horizontal rotation minimum
21. type = entity ID (only available for @r and @e)

Added in 1.9

1. tag = scoreboard "tag" stored on the target (via Tags list, modifiable with /scoreboard players tag <target> <add|remove> <tagname> {dataTags})