Many games use weapons as a way to boost the strength of the characters in the game. Weapons often play a pivotal role in the play style and mechanics of the game. When games weapons have depth and verity, they help to give the player options when it comes to playing and customizing there character.
Because of the importance of weapons in games, many designers use weapon upgrades as a way to extend the use of a weapon in game. Designers can approach this in many different ways, one ways in through mini quests. When games require the player to fulfill a list of requirement before a weapon can progress, allows the player to have mini goals in their game play. This also makes weapon progression more interesting than a simple buy and apply mechanic.
In Destiny, any weapon above the color gray, has the ability to be upgraded. These upgrades have a large range of abilities and require the weapon to be used in order to be upgraded. This means that the more the use the weapon, the stronger it becomes. This creates and interesting and unique weapon selection process for the players.
Example 2: The Divison.
It Tom Clancy's Divison, Players are able to upgrade their weapons by using attachments, mods, etc. The weapon mods and attachments can be gained by doing missions, side quests, or even craft the parts by using blueprints. In this way, players can have fun creating different builds to use during game plays.