I'm making a top-down action game. Should I use Rigidbody2D for collision even though I won't be using physics otherwise?

Questions & Answers
1

It seems like a waste to make everything into a physics object just to handle collision detection (basically I just don’t want things passing though each other and detection for getting hit with player and enemy attacks), but on the other hand, from what I’ve been reading setting up collision detection without using RigidBody is much more complicated. Any suggestions?

2

So, I totally lied to you.

That being said, this still does not mean you need all of your objects to be physics based items.

The objects you want your character to not be able to pass through only need colliders.

However, you will need your character to have both a rigid body and a collider to trigger the oncollision event.

As to your question in the earlier comments, you will not need to code any type of system to keep your character from passing through objects. This is something colliders do intrinsically.

Having said that, you may want other things that will exist in large numbers, to enact a function when impacting an object without each of these instances undergoing physics updates.

In such cases, you can do something like this:

    Transform m_Transform;
    SphereCollider m_Collider;

	void Start () 
    {
        m_Transform = GetComponent<Transform>();
        m_Collider = GetComponent<SphereCollider>();
	}
	
	void Update () 
    {
        if (Physics.OverlapSphere(m_Transform.position, m_Collider.radius).Length <= 1)
            m_Transform.localPosition += (Vector3.forward * Time.deltaTime);
        else
            Explode();
	}

This will allow you to avoid calling fixed update every 0.02 seconds and still have things like projectiles impact targets.