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Basically, I've taken the current badges on StackOverflow, and broke them into actions you can perform on the site. (Posting, Editing, etc).
Once I decided on the actions, I gave each action a gold, silver, and bronze badge, and saw which badges actually fit into those categories.
This left me with a list that shows which site actions don't have certain levels of badges in them. I'm not saying that we should put these badges in place, I'm just giving an overview of where the disconnects are.
Posting Question Views [b] Popular Question - Asked a question with 1,000 views [s] Notable Question - Asked a question with 2,500 views [g] Famous Question - Asked a question with 10,000 views Votes [b] Student - Asked first question with at least one up vote [b] Nice Question - Question with score of 10 or more [s] Good Question - Question with score of 25 or more [g] Great Question - Question with score of 100 or more Favorite [b] [s] Favorite Question - Question favorited by 25 users [g] Stellar Question - Question favorited by 100 users Tagging [b] [s] Taxonomist - Created a tag used by 50 questions [g] Answers Votes [b] Nice Answer - Answer with score of 10 or more [s] Good Answer - Answer with score of 25 or more [g] Great Answer - Answer with score of 100 or more [b] Teacher - Answered first question with at least one up vote [s] Enlightened - First answer was accepted with at least 10 up votes [s] Guru - Accepted answer and voted up 40 times [g] Commenting [b] Commentator - Left 10 comments [s] Pundit - Left 10 comments with a score of 5 or more [g] Bounty [b] Altruist - First bounty you manually awarded on another person's question [b] Benefactor - First bounty you manually awarded on your own question [b] Investor - First bounty you offered on another person's question [b] Promoter - First bounty you offered on your own question [s] [g] Low-vote accepted answers [b] [s] Tenacious - Zero score accepted answers: more than 5 and 20% of total [g] Unsung Hero - Zero score accepted answers: more than 10 and 25% of total Reviewing Voting [b] Supporter - First upvote [b] Critic - First downvote [s] Civic Duty - Voted 300 times [g] Electorate - Voted on 600 questions and 25% or more of total votes are on questions Editing [b] Editor - First edit [s] Strunk & White - Edited 80 posts [g] Copy Editor - Edited 500 posts Retagging [b] Organizer - First retag [s] [g] Rollback [b] Cleanup - First rollback [s] [g] Flagging [b] Citizen Patrol - First flagged post [s] Deputy - Raised 80 helpful flags [g] Marshal - Raised 500 helpful flags Deleting [b] Disciplined - Deleted own post with score of 3 or higher [b] Peer Pressure - Deleted own post with score of -3 or lower [s] [g] Site Viewing [b] [s] Enthusiast - Visited the site for 30 consecutive days [g] Fanatic - Visited the site each day for 100 consecutive days Reputation [b] Mortarboard - Hit the daily reputation cap for the first time [s] Epic - Hit the reputation cap of 50 days [g] Legendary - Hit the daily reputation cap on 150 days Membership [b] Autobiographer - Completed "About Me" section of user profile. [s] Beta - Actively participated in the Stack Overflow private beta [s] Yearling - Active member for a year, earning at least 200 reputation [g] Misc [b] Scholar - First accepted answer on your own question [b] Self-Learner - Answered your own question with at least 3 up votes [b] Tumbleweed - Asked a question with no answers, no comments, and low views for a week [s] Generalist - Provided non-wiki answers of 15 total score in 20 of top 40 tags [s] Necromancer - Answered a question more than 60 days later with a score of at least 5 [g] Populist - Provided an answer that outscored an accepted answer with 10 votes by 2x [g] Reversal - Provided answer of +20 score to a question of -5 score
Hopefully this may be of use to someone.