Ten Challenges I Love in Games

These are the sorts of things I try to combine when running my own games, and the sorts of things I love to see as a player. You can see a significant throughline-- solving a problem where the default method will result in failure. 

1. Communicating with some who doesn't share a language with you. When given the time and space to do so, playing charades with an NPC or trying to find common terms fully engages me, and makes me identify strongly with that NPC, since this kind of interaction is a rare example of intimacy between strangers.
2. Communicating with someone who has very different basic assumptions from you. This works for the assumptions of the PCs or of the players. It is why I find it so rewarding to spend time giving the folk inhabiting the setting a properly non-modern mindset, and why many GMs are keen on the "Medieval Mindset" in particular. It makes every encounter an example of negotiating different assumptions.
3. Fighting something that cannot be harmed by typical means. Many OSR games feature monsters too strong to fight, but other variations work too, and enforces that a problem exists to be solved rather than powered through.
4. Outsmarting attempts to make you violate a Rule with Fierce Consequences. Taboos and transgressions are interesting themes to me, and imbues the setting itself with some kind of linguistic characterization.
5. Piecing together a mystery from disparate sources of information. Trying to understand people long-dead based on the extant artifacts still found in our time. Noticing patterns. Inferring and stepping around biases, ancient and modern.
6. Evading something dangerous. Usually requires exploration. Reminds me as a player that the world is not just an arena for interaction with NPCs and monsters, but a challenge in itself. often gives a concrete reward of understanding how something is laid-out or where something is.
7. Locating something hidden with clever deduction. Sort of a combination of the previous two, but feels very different to me. Looking at the negative spaces in an area and applying sense to where they might be filled in.
8. Making trade-offs for the people you are responsible to. Problems with no solution, that are only difficult because they have a cost. Shows the relationship between PCs and the society they keep. Many players are brave in risking the lives of their characters, or of unattached NPCs, but it can be a different game when people who depend on them are affected by their decisions.
9. Evoking a real-life sensory experience for how your characters enjoy a meal or other pleasant experience. Redwall feasts, that kind of thing. This kind of challenge is offered, without penalty or in-game advantage. It creates small moments, pleasant moments, opportunities to appreciate. 
10. Creating art. I believe that creating is, by default, good for someone. That when a player writes a poem about their adventures, or when their character designs a coat of arms, or the party christens itself with some self-deprecating name, the game is elevated. It does not matter how technically accomplished any of these small pieces of art are. Accordingly, I want to encourage and create opportunities for descriptions, crafts, poetry, prose, jokes, and the like.