Builds. Build builds builds. Whether its slowly tailoring your class to a build, or roguelike unlocking items and abilities to build around each run. It's why I like things such as Diablo, PoE, Last Epoch, Binding of Isaac, Tales of Maj'Eyal, Neverwinter Nights, Baldur's Gate, etc.

Its also why I was severely disappointed with ArcheAge. And unhappy when I returned to GW2 to find my world bossing combat medic off-meta bleed Warrior pretty much useless. Used to tank boss AoEs to revive downed people using healing shouts and increased revival speed. They nerfed and removed the revival speed node from Warrior and the build lost half it's function.

I like strategy games that allow you to design your own units such as Warzone 2100 where you select different components to get different functionality or Endless Space 2 where you pick a ship hull type and then assign different modules to adjust the combat stats or add special abilities. The production cost of the unit changes with your selections in whatever the base game currency is and/or requirements for specific resources.

This gives the player the freedom to adjust their forces to fit their play style, their economic situation or to accomplish specific objectives or strategies. It also breaks the rock/paper/scissors aspects of unit combat in more simplistic games and creates far more complex unit interactions, and the potential to win with clever design rather than just numbers of units.

Hard to learn complex mechanics in simulation, such as target management analysis in dangerous waters, any of the jobs in space station 13, eve online

Dynamic skill leveling: maybe it's not an actual stat with a number you can watch go up as you keep using a particular play style, but I like when games let you and your gear get stronger together the more you use them.

I'm a sucker for crafting and breeding systems that allow you to customise equipment and/or characters. But it's really hard to find good implementations of the idea, most have some obvious flaw:

• Pokémon (breeding) - in early games RNG plays too much of a role, so it's hard to get what you want. Late games don't fix this, instead they allow you to skip the process altogether (see: hyper training).
• Niche - the breeding part of the game is actually really good, a shame that the rest of the game is a slop. For example gathering food gets a PITA once you got too many nichelings, and yet you want them to support your breeding pairs.
• RimWorld (Biotech; germline genes) - arbitrary restrictions that must be lifted through the usage of mods.
• RimWorld (crafting) - now we're talking. If you pay close attention to which materials you're using for which tasks, it pays off in the long run. There's some luck involved, but you can get perfect (legendary) stuff fairly often if you know what you're doing.
• Leaf Blower Revolution (leaf crafting) - the game encourages you to craft a lot of leaves and salvage most of them. That's fine, it's easy to get cheese anyway. The problem is the sheer amount of beer that you need to get the properties that you want in each leaf.
• Monster Breeder (old Flash game) - the game is a bugfest, and the lack of any sorting system makes you have a hard time even knowing which monster you should be breeding with which.
• Minecraft (tools and weapons) - vanilla has a really dumb system that doesn't fit well in a game that encourages hoarding piles of materials into chests. The mod Tinkers' Construct fixes this, and makes the system next to ideal.

Plus a lot more that I didn't mention. Sorry for the wall of text.

I've very rarely disliked "prepping". For example building boss arenas in Terraria or setting up my equipment for a hunt in Monster Hunter or learning about the monsters in Witcher 3. Anything that lets me prepare for future encounters is a system I enjoy, even if it's only superficial.

I hate it only when it's turned into somekind of a survival element that exists solely for the purpose of resource management. For example I hated hunger and water in Subnautica. From a certain point forward those two things become just mindless busywork because when you plant it in your base it just grows and whenever you need to fill up you just go to your base and eat and drink and there's no upside nor a real downside to those two mechanics.

I'm currently a big fan of the 'trading' enemies and then planning your attacks system in Sniper Elite.

I love the histogram system from Zachtronics' games. I find it much more useful to see my score compared to the proportion of people who got a similar score, than a leaderboard rank that doesn't mean much.

Broadly speaking, I enjoy stealth in games as long as it's implemented correctly and doesn't break the game or function poorly and leave you at a disadvantage. Despite the many qualms I have with tlou2, the added mechanic of going prone and all the upgrades associated with stealth was quite fun—and, of course, the functionality of the bow and arrow, and how you can conserve ammo. Parsing an area with dogs and navigating their heightened scent through long grass and deciding when to pick off certain enemies or ninja though is tremendously fun for me.

Desperados III and Shadow Tactics are two other stealth games that I love that use a design similar to The Commandos series. You can navigate through their detailed environments deciphering a path through on your own, using whichever abilities your party has to your advantage. I think the ninja/feudal Japan game world fits better with Shadow Tactics (I also prefer the characters) but Desperados III has just as good, if not better level design.

To add a somewhat weird one, I'll say a good save feature. Saving with an ink ribbon in RE was so freaking awesome—especially in regards to how it adds a level of complexity to item management. Another cool example that doesn't add anything to gameplay but was neat: ICO and how you save your game with Yorda on the couch. So wholesome; I can hear the music in my head, even.

E: Also, Demon's Souls' character and world tendency mechanics were so incredibly imaginative. The fact that you can unknowingly die too many times in human form, turn an area into black world tendency, and get eviscerated by black phantoms for seemingly no reason is wildly brutal and awesome.

With a few exceptions all the games I have played in the last 10 years have one thing in common - open world. Then again I have mostly played only Dayz/Arma, Rust and Space Engineers.