Is there a way to show collision in-game?

I’d like a way to make my collision boxes become visible in the game mode so I can test and find problems easier.

Use wireframe gizmos, then toggle so that they are visible in the game view

for example :

#pragma strict

#if UNITY_EDITOR

function OnDrawGizmos()
{
	Gizmos.color = Color.yellow;
	
	var col : BoxCollider = GetComponent.< BoxCollider >();
	
	if ( col )
	{
		Gizmos.matrix = transform.localToWorldMatrix;
		Gizmos.DrawWireCube( Vector3.zero + col.center, col.size );
	}
}
	
#endif

Not exactly - however, view your game in the scene view while playing - have both scene and game views visible and you will be able to visualise everything.