Well we are coding a Zelda type clone and I'm still working on my space sim as well. I'm not sure I can do either of these without some type of significant scripting in place to do missions, quests, etc.
Now for something simple you might be able to get away with using functions as script actions but again I shudder at doing this because it really hard-codes you into a corner later on.
At the very least you could implement a variable system and some IFs. A variable system can be implemented by using a class to wrap access to an array of values. It's quite simple and then you use script commands to access and modify the array.
This prevents you from having to create a difficult expression parser which is really not needed for most applications of scripting. We are not trying to re-write the C++ parser here, just something basic.