I can think of a few…
3D6 Per Ability.
No leeway in score variation. Extremely Limited customizability. Closest to reality.
(Ex: Rolling for each ability individually, 3d6 hard core.)
4d6 –Lowest; Per Ability
No leeway in score variation. Extremely Limited customizability. Closer to reality.
(Ex: Rolling for each ability individually, 4d6 not counting lowest die roll)
4d6 –Lowest; Free Assign (Core Rules)
Little leeway in score variation. Limited customizability.
(Ex: Rolling a set of 6 numbers, 4d6 not counting lowest die roll, and assigning them freely)
Base + Sliding Scale
Good leeway in score variation. Medium customizability.
(Ex: 10 in all abilities and 24 Points to assign; -1/-7 are +1:1; +1/+3 are -1:1; +4/+6 -2:1; +7/+8 -3:1)
(an 18 would cost 13 points!)
Base + Non-Sliding Scale
Highest leeway in score variation. Highest customizability.
(Ex: 3 in all abilities and ~60 Points to assign; 1:1)
(an 18 Cost 15 Points)
Other
3D6 Per Ability.
No leeway in score variation. Extremely Limited customizability. Closest to reality.
(Ex: Rolling for each ability individually, 3d6 hard core.)
4d6 –Lowest; Per Ability
No leeway in score variation. Extremely Limited customizability. Closer to reality.
(Ex: Rolling for each ability individually, 4d6 not counting lowest die roll)
4d6 –Lowest; Free Assign (Core Rules)
Little leeway in score variation. Limited customizability.
(Ex: Rolling a set of 6 numbers, 4d6 not counting lowest die roll, and assigning them freely)
Base + Sliding Scale
Good leeway in score variation. Medium customizability.
(Ex: 10 in all abilities and 24 Points to assign; -1/-7 are +1:1; +1/+3 are -1:1; +4/+6 -2:1; +7/+8 -3:1)
(an 18 would cost 13 points!)
Base + Non-Sliding Scale
Highest leeway in score variation. Highest customizability.
(Ex: 3 in all abilities and ~60 Points to assign; 1:1)
(an 18 Cost 15 Points)
Other