Tranquilities, Dark Side of the Cache, Any year's Limited Edition versions of the Compass Rose Geocoins expecially the Yemon Yime Versions, AE versions of Popular geocoins (mainly because of the low minting numbers), Event Versions of Popular geocoins (Such as MOGA, GCF, MWGB etc). All of these tend to have higher than normal collectible value/$ value but like many collectibles, it goes up and down depending on supply and demand. The one that I see consistently retain a high value is the Yemon Yime Compass Rose versions (usually only minted in 42 or 21 geocoins per version). Yemon Yime rarely sells them (usually only for charity purposes) and generally gives them out to others as gifts or trades. The low minting numbers mean that few people end up with duplicates and rarely trade out of their collections increasing the rarity of getting one. The tranquility geocoins are the same but with 38 versions and hundreds minted, they still are more readily available for purchase/trade. The moun10bike coins are valuable for trade/collection because of the geocaching historical value of having one. Most of the versions of Moun10bike geocoins have been minted in the thousands of geocoins so they aren't rare because of there is not many of them but because most people don't want to let go a part of geocaching history. My first geocoin designed and minted by geocoinstore.com sold roughly 100 geocoins each version and was not considered a great seller but currently fetch $40-$60 on eBay with the AE version (25 minted) getting $50-$75. I have seen Tranquility Geocoins list as $100 - $180 as a buy it now option but when listed as an auction format go anywhere from $40 - $80 dollars. Most of the values go up and down like any other collectible.