Rare Achievements

Is there a list anywhere of what achievements are classified as 'rare'?

All of them?  No.

You can check individually for each game under its achievements page.  Rare achievements are in purple text.

Why bother with a list? The list would change over time, as it's based on members who have played the game and those who unlocked the achievement... or is it xbl members total vs. how many unlocked it?

At least that's how I understood it.

You can sort your own achievements from most rare to most common. My most rare is only held buy 10 people. Pretty cool.

My most rare is held only by myself. I'm #1

http://www.giantbomb.com/achievements/nothing-to-see-here/1425/

The rarity of achievements, and thus your grade per game, is determined by the entirety of people here on Giant Bomb using the application. The only exception is getting all points gets you an S-rank. A good example is that I only have 45 points in F.E.A.R. but that's enough to warrant a C rating. Probably because the points in that game are so impossibly hard to get. Another good example is that just about all of my achievements from the "Raising Hell" expansion to Overlord are rare. I guess no one downloaded that.

I'm going to be curious how the achievements for Operation: Darkness rank up. I finally managed to find a copy of that.

In MLB Front Office Manager I have 14 achievements where I am the only person who has them.

Guess nobody else was as jazzed as I was to click through menu screens for 20+ hours......

MINE STILL HASN'T LOADED. OMGWTFBBQ. Seriously though I wonder if the veteran achievements for cod4 are rare. That game was hell to beat on vet.

I really like how the grades work.

For example I have all the singleplayer achievements for The Darkness and Chronicles of Riddick: Dark Athena, but I have not touched the awkward unnecessary multilayer components. What do I get for both titles?
"A"

It's nice and it makes sense. Perhaps developers can see the lack of people trying different modes on their games and take a hint.

I have 36 rares. Word.

I have about 40 rares. Those MK vs. DCU Kombo Challenges really paid off, it seems.

663 rares. BAM!

Rarity is based on people on Giant Bomb that have played that game. If less then 10% of the users who have that game have that achievement we classify it as rare. If less then 30% have that achievement, it is classified as uncommon.

^ can tell your a virgin when.....

I think I have 20 something rares.

Kameo, Banjo, PDZ, Viva Pinata, Trouble in Paradise, and Jetpac: Refueled.

About 12 rares or so. A majority of them came from Assassin's Creed involving with those bloody flags. I think I've got two from Grand Theft Auto IV with the pigeons and 100% completion.

Unfortunately looks like the veteran achievements on Call of Duty 4 doesn't warrant a rare yet. Infinity Ward last gave us a report that only about 3% has the Mile High Club achievement out of 10-14 million players, of course most of us are a bit more hardcore than the causal players.

I have like 26, there's a lot of people who don't have Halo 3 DLC :P

It would be cool if you could sort through a leaderboard for rare achievements.

So far I'm the only person on GB with max points in Ninja Gaiden 2 and Street Fighter 4 :)