My first idea is making multiple lists inside the list for every different game object, but this doesn't seem very practical.
I am sure you have better ideas.

There's nothing particularly impractical about having type-specific lists as well as a list of all entities, particularly for a small game. Simple, pragmatic approaches often a good idea, not least because they're easier to replace when you have a clear picture of where the bottlenecks are.

If you have a particular issue which has come up in profiling (e.g. iterating through all enemies is taking too much frame time) or that you know you're going to face (e.g. you're trying to push the envelope in terms of number of opponents), then that's the time to start looking for other, more complicated approaches, like spatial hashing for instance.

Out of curiosity.. Why are you using a list? Why not a std::vector? A std::vector has better performance than a std::list, and I'm not only talking about memory usage, a std::vector is actually much faster than a std::list. (CPU caching and such)

A further explanation is here:
http://channel9.msdn...rup-Cpp11-Style

Skip to around 44 minutes, he gets into it at like 44:40. (Although I recommend watching all of it, if you haven't)

Alright, that helps me.

I have run into another problem though.
Since the hierarchy manager will have functions that returns objects of a ceirtain requested type, would it be a good idea to keep a different list for each object type? Iterating through all objects and checking their type seems pretty slow to me.

Although it may be complicated, this can be achieved through mapping each type of GameObject to an index in an array.
I realise that sentence doesn't make all that much sense, but I'll try to explain it further.
Basically this may be a way of storing your GameObjects:

std::vector<std::vector<GameObject*> > gameObjects;


Where the first index is the GameObject's class type ID, and the second index is the GameObject's ID, or vise versia (1st = GAMEOBJECT_ID and 2nd = TYPE_ID)
i.e.

gameObjects[TYPE_ID][GAMEOBJECT_ID]
// or
gameObjects[GAMEOBJECT_ID][TYPE_ID] // this way may be more efficient, since there is more GameObject objects than there is GameObject classes


This means you will need to store an ID in the GameObject, and register the ID when you add the GameObject.

Now to store/get the TYPE_ID of a GameObject calss is possible without the use of RTTI you just need to think hard (you can do it with virtual functions and macros; using virtual functions since you need to know what type a GameObject is). Currently, I am doing something similiar (storing objects by type) by using macros that are defined WITHIN each class.

For example, here's what a class that derives a GameObject may look like:

class Player : public GameObject
{
// registers the class, adds an ID to the game object CLASS
// also defines virtual/staitc functions to retrieve class information (ID, name, etc.)
REGISTER_CLASS(Player)
public:
};

Then.. to access a game object it may be something like this:

template <typename Type>
Type* getGameObject(int id)
{
return gameObjects[typename Type::GetClass().getId()][id];
}
// or...
GameObject* getGameObject(const GameObject::Class& gameObjectClassType, int id)
{
return gameObject[gameObjectClassType.getId()][id];
}

Of course, I don't really want to give it away all that much, and there is probably another method of doing this (through the use of templates)