Hitman is one of those games that the more you play, the more items you will earn. There are a ton of people who don't really have anything to start each mission out with because they think that you can only find certain things within each mission. There are actually a ton of weapons, gear, and even outfits that you can permanently unlock for use in everything the game offers, other than the limited missions.
There are a total of 4 main ways to permanently unlock weapons and gear, and those are through map mastery unlocks, escalation contracts, silent assassin/suit only objectives, and elusive targets. Each has its own requirements to get and challenges to complete to earn all sorts of cool gear to use later on.
We will quickly explain each one and what type of items they generally give you. Just keep in mind that certain ways are harder to complete than others.
Map Mastery Unlocks
There are a total of 20 mastery levels to complete for each map and there are a total of 21 maps to complete, as of this article, if you own the entire trilogy. These levels aren't that difficult to get through because all you need to do is complete the mission and it will level up the mastery.
Half of the stuff you get from the mastery levels is usually related to that specific map only, but the other half are items you can use wherever and whenever you want to. Just play the game and you will unlock all sorts of cool weapons, gear, and outfits to use.
Escalation Contracts
All maps in the entire trilogy have missions called escalation contracts. There are usually 3 parts to them and they get progressively harder as you complete them. Generally, you will get some really nice gear after completing the first mission, so don't worry if you think the rest of the missions are too difficult for you to complete.
There is some really great gear to unlock through these missions, and you don't even need to play them all to get free stuff, just keep in mind that the missions are usually not that easy to complete.
Silent Assassin / Suit Only Objectives
These are our favorite challenges in the game because they require you to complete any mission by not being seen and also never changing your starting outfit. There are more like sniper assassin that is fun as well, but if you complete a certain number of missions with extreme stealth, then you will unlock some really cool classic gear.
You can get a classic suit, coin, sniper, fiber wire, briefcase, and lockpick if you complete all the needed missions, and is definitely worth doing.It is one of the hardest but most fun challenges in the entire Hitman trilogy.
Elusive Targets
Most people who play Hitman have probably not tried to complete an Elusive Target. You only have one chance to complete your mission and you need to use your detective skills to try and find them in the world. You can restart the mission as long as you haven't killed your target yet. Once you kill them, you only have one chance.
Elusive Targets only give you suits to use, so if you like having new outfits to use or you want to flex on how many targets you killed, then you might want to check out the Elusive Target Arcade which they recently added to Hitman 3.