Well, to be honest that's a really vague and kind of unanswerable question.
All the entities have different functions, and the majority of them you will neverr need to use.
The DoD tutorials will show you everything you need to have to make your map work for Day of Defeat: Source, particularly this one you are posting in, and beyond that well...it all depends in what you want to do with your map.
I don't really think you should build a map around a particular entity, and there aren't really any that should have a map built to showcase them. It's really more about what you want to accomplish, what effects you want to achieve. Think more about location and them and then look for tutorials and ask questions about achieving the effects you want.
There are, however, some entities that you do need to have. First off, func_detail.
This is a brush based entity (a brush is a physical, geometric object like a box or a wall). If you build some complicated geometry, like small details rather than halls and floors, then you will want to tie the brush(es)[/i[ to a func_detail by clicking the toEntity button and selecting func_detail from the list.
Then there is the light, light_environment, light_spot, and light_dynamic entities. Obviously these are lights! The light entity is a spot in space that projects light in all directions, the light_environment is an entity that lights up all the areas of your map that are [i]seen by the skybox, the light_spot is like a spotlight and casts a cone of light, and the light_dynamic you probably don't need to worry about.
Then there is the env_cubemap. This is used to help the game create reflections on shiny things. There are a couple tutorials here about using them.
Next up is the water_lod_control, which is essential if you have water in yout map. Once again, I believe there is a tutorial here about using it.
Obviously, you have to have spawn points.
Then there are the prop_* entities. (we usually use a * to indicate something that has many options, for example, prop_physics, prop_static, etc.)
The prop_static and the prop_physics_multiplayer are the two you are most likely to use. prop_static is for things like pipes, doors, and some architecture, which don't move. prop_physics is for things like crates and barrels that can be pushed around and sometimes broken. I forgot to mention that a prop is a model made in another program. Once you placve the entity, press shift+s to get back to the selection tool, and the alt+enter to bring up it's properties. Select "World Model" on the left and then click browse on the right to select your prop. Not all models can be used with all prop_* entities though.
And after that, just ask questions about different results and effects you are trying to achieve in your map.
And good luck!





