Trinkets
Warning: Spoilers
This page or section contains unmarked spoilers from update 1.6 of Stardew Valley. Players may want to avoid or be cautious toward reading this article/section. 
Trinkets are equippable clothing items. Each one of them gives the Player unique benefits. They can be found after Combat Mastery is claimed. Most trinkets can be dropped by monsters, found in crates and barrels in the Mines, Skull Cavern, and Quarry Mine, or obtained in Skull Cavern treasure rooms. The Magic Hair Gel is the exception, as it can only be purchased from Alex's shop in the Desert Festival.
The player can obtain the same trinket multiple times. Trinkets do not stack. They can be sold at the Adventurer's Guild for 1,000g each.
All Trinkets, with the exceptions of the Basilisk Paw and the Magic Hair Gel, can be reforged on an Anvil. This randomizes their stats and costs 3 Iridium Bars per reroll.
Trinket List
Image  Name  ReForged Stat  Max Stat  Description  Source  Sell Price 

Basilisk Paw  N/A  N/A  You are immune to debuffs. 

1,000g  
Fairy Box  Level  5  Summons a level X fairy companion that heals you in combat situations. 

1,000g  
Frog Egg  Color  N/A  Summons a hungry frog companion. 

1,000g  
Golden Spur  Duration  10 Seconds  Critical strikes give you a speed boost for X seconds. 

1,000g  
Ice Rod  Frequency; Duration 
3 Seconds (min); 4 Seconds 
Shoots an orb of ice every X seconds, freezing any enemies in its path for Y seconds. 

1,000g  
Magic Hair Gel  N/A  N/A  Your hair shimmers with all the colors of a prismatic shard. 

1,000g  
Magic Quiver  Type: (None), Perfect, Rapid, Heavy  Varies by Type  Shoots a magic arrow at nearby enemies every X seconds, dealing YZ damage. 

1,000g  
Parrot Egg  Level  4  Summons a level X parrot companion, who grants you a Y chance to find gold coins when slaying monsters. 

1,000g 
Drop Chances
All trinkets, other than the Magic Hair Gel, have a 0.63% chance to be found in a Skull Cavern treasure chest. If the player has not yet claimed Farming Mastery, then the chance is 0.64% for each trinket.^{[1]} Calculations for the drop rates from monsters and containers are more complex and depend on several factors.^{[2]}
Monsters
When slain, all monsters have a chance to drop a random trinket that is not the Magic Hair Gel. This is calculated as follows:
 Every monster starts with a base chance of 0.4%.
 Every point of maximum health will add an additional 0.001% to the base chance.^{[3]}
 After adding the monster's max health, its category is considered:^{[3]}
 If it is classified as a "Glider" (flying enemy) and its max health ≥ 150, then 0.2% is added to the drop chance. This condition is applied to Iridium Bats, Bats (dangerous), Lava Bats (dangerous), Haunted Skulls, Haunted Skulls (dangerous), Cave Flies (dangerous), Carbon Ghosts, Putrid Ghosts, Squid Kids (dangerous), Bugs (dangerous), Armored Bugs (dangerous), Serpents, Royal Serpents, Magma Sprites, Magma Sparkers, Dwarvish Sentries, and Blue Squids.^{[4]}
 If it is classified as a "Leaper", then 0.5% is subtracted from the drop chance. This condition is only applied to Spiders.
 After considering all of the above, the chance is the minimum between the calculated value and 2.5%. The theoretical maximum chance at this point is 2.5%. In reality, the calculated chance usually ranges from 0.1% (Spider) to 1.65% (Royal Serpent with 18 tail segments).
 The player's daily luck is now added via the following formula:
baseChance += Game1.player.DailyLuck / 25.0
. Daily luck ranges from 0.1 (unlucky) to 0.1 (lucky), and the value is increased by 0.025 with the Special Charm. At worst (no Special Charm, worst luck day), the chance is decreased by 0.4%.
 At best (Special Charm, best luck day), the chance is increased by 0.5%.
 Finally, the player's luck buffs are added via the following formula:
baseChance += Game1.player.LuckLevel * 0.00133)
. Every point of luck (via food, rings, etc.) will add 0.133% to the drop chance.
Trinkets are not directly added to a monster's drop pool; they are spawned separately. This means that the Burglar's Ring and Monster Compendium will not affect the chance for or number of trinkets dropped.
Crates and Barrels
Breakable containers in the Mines, Skull Cavern, and Quarry Mine have a chance to drop a random trinket that is not the Magic Hair Gel. This is calculated as follows:
 Every container starts with a base chance of 0.4%.
 The player's daily luck is added via the following formula:
baseChance += Game1.player.DailyLuck / 25.0
. Daily luck ranges from 0.1 (unlucky) to 0.1 (lucky), and the value is increased by 0.025 with the Special Charm. At worst (no Special Charm, worst luck day), the chance is decreased by 0.4%.
 At best (Special Charm, best luck day), the chance is increased by 0.5%.
 The player's luck buffs are added via the following formula:
baseChance += Game1.player.LuckLevel * 0.00133)
. Every point of luck (via food, rings, etc.) will add 0.133% to the drop chance.  Finally, the chance is multiplied by a chance modifier, which is calculated via the following formula:
1.0 + effectiveMineLevel * 0.001
. The location of the crate or barrel will determine the effective mine level: In the Mines, the effective mine level ranges from 1 to 120 and corresponds with the actual floors. Thus, the chance modifier ranges from 1.001 to 1.120.
 In the Skull Cavern, the effective mine level starts at 121 (on the first floor) and increases by 1 for each additional floor. Thus, the chance modifier starts at 1.121 and steadily increases as the player goes deeper into the cavern.
 In the Quarry Mine, the effective mine level is set to 5000. Thus, the chance modifier is 6.0.
The difficulty levels of the Mines and Skull Cavern do not affect the drop rates from containers in each location.
Bugs
 Although trinkets can be gifted, they do not appear in the Gift Log.
References
 ↑ See MineShaft::getTreasureRoomItem in the game code.
 ↑ See Trinket::TrySpawnTrinket in the game code. Chances are determined in GameLocation::monsterDrop and BreakableContainer::releaseContents.
 ↑ ^{3.0} ^{3.1} Base health and glider categorization can be found in Data\Monsters.xnb.
 ↑ Ghosts are coded as gliders in Ghost.cs.
History
 1.6: Introduced.