Prerequisites: Base attack bonus +0.
Special: This feat can be taken multiple times. Each additional 1d6 of extra damage requires a higher base attack bonus.
1d6: +0 2d6: +2 3d6: +3 4d6: +5 5d6: +6 6d6: +8 7d6: +9 8d6: +11 9d6: +12 10d6: +14
Sneak Attack, an ability associated with the rogue core class, is used across a myriad of other classes and prestige classes in modified form. Bonus damage typically stacks, unless the ability is renamed.
Classless limits: Experience rank? (+1 at 1st level and increases by +1 every 4 levels thereafter)
Bonuses do stack.
Highland stalker: 2nd, 4th, 6th, 8th, and 10th level.
Ninja: 1st, 3rd, 5th, 7th, 9th, 11th, 13th, 15th, 17th, and 19th level.
Ghost-faced Killer: 2nd, 5th, and 8th level.
Sneak attack is a combat ability but classes tend to gain its benefits regardless of being especially stealthy or dexterous. Its being gated behind base attack bonus to represent this nature. Any character can gain it at first level, but improving it depends on how their attack bonus progresses. A rogue-like character with a little combat focus can gain it every two levels. A wizard-like character with only a basic (poor) base attack bonus would struggle to gain sneak attack as few as seven times in twenty levels.
Wizard 1st +0 +1d6 4th +2 +2d6 6th +3 +3d6 10th +5 +4d6 12th +6 +5d6 16th +8 +6d6 18th +9 +7d6