Age of Fear 2: the Chaos Lord. Actually the whole franchise (4 games), but this is the one I started with.
Tactical turn-based combat, viewed to-down, combined with a Fantasy setting.The storyline is not the deepest, but the characters have strong personalities and the narrative is voiced, which was unexpected from a dev team this small. To me there's a mild Terry Pratchett feel to these games as well, which is always a positive.
The gameplay is very free and open, there are main missions, side-missions, and pure combat missions (for levelling up). There are random events as well.The focus of the game is the combat, even though it does have some RPG elements. So I see these games more as tactical combat games rather than RPGs.
The combat is really fun and so well done; you build your own squad or army, that changes over time as some of them will die and need to be replaced. You feel the loss when a high-level soldier dies, and you really need to learn each unit type's strengths. All units can be upgraded and specialized in a few different ways. You need to have a good mix, as you will face a wide range of enemy types.
Another cool thing is the interconnection between all the playable characters, for example playing as the Orc warrior you will come across the other playable characters in the series during your campaign, which I think is a really cool idea.It makes not only each game feel alive and grounded, but also the whole franchise, which I have come to see as "one unit" despite being separate games.They all take place in the same universe.
This game, and all in the franchise, really are a labour of love for the devs. It's a phrase that often gets thrown around, but in this case it is very much true. The devs will actually go back to their previous games and update them with stuff that was made for the later games. So every game in the franchise is continously improved and expanded upon with time. For example , they recently backported crafting to the older games in the series. To me that kind of commitment to their older games is really impressive, you don't see triple-A studios doing that, or most Indie games for that matter.
There are many other games I could have picked but it's the latter that really elevates this game and franchise above other Indie games for me. And it's really unfortunate these games are not on GOG (yet?).