In this example if from a tile set of 2D sprites. Each tile checks to find its neighbor tiles.
I use 0.32 as offset in each direction since my sprite is 32px.
var marketArea : Collider2D[] = Physics2D.OverlapAreaAll( Vector2(transform.position.x-0.32, transform.position.y-0.32), Vector2(transform.position.x+0.32, transform.position.y+0.32) );
for (var i = 0; i < marketArea.Length; i++) {
//Here I test it the collider next to the sprite has a tileBehaviour script
// you could test for other things like tag or name
if(marketArea*.GetComponent(tileBehaviour) ){*