Change items..

public void switchItemSlots(int index) {
        if(inventorySlots.Count > index) {
            if(switchRightHandItem) { //if it's right hands turn
                if(inventorySlots.IndexOf(currentItemRight) != index) { //if the chosen slot is different than our current item's slot.
                    if(currentItemLeft == null) { //if there is nothing on the left hand
                        if(currentItemRight != null) {
                            currentItemRight.SetActive(false);
                        }
                        inventorySlots[index].SetActive(true);
                        setCurrentItemRight(inventorySlots[index]);
                        invGui.ChangeHighlight(currentItemRight);
                        currentItemRight.GetComponent<Rigidbody> ().useGravity = false;
                        foreach (BoxCollider col in currentItemRight.GetComponentsInChildren<BoxCollider>()) {
                            col.enabled = false;
                        }
                    } else { //if left hand has something
                        if(inventorySlots.IndexOf(currentItemLeft) != index) {
                            if(currentItemRight != null) {
                                currentItemRight.SetActive(false);
                            }
                            inventorySlots[index].SetActive(true);
                            setCurrentItemRight(inventorySlots[index]);
                            invGui.ChangeHighlight(currentItemRight);
                            currentItemRight.GetComponent<Rigidbody> ().useGravity = false;
                            foreach (BoxCollider col in currentItemRight.GetComponentsInChildren<BoxCollider>()) {
                                col.enabled = false;
                            }
                        } else {
                            tempSlot = currentItemLeft;
                            currentItemLeft = currentItemRight;
                            currentItemRight = tempSlot;
                        }
                    }
                } else { //if player tries to change current weapon to a same weapon (same slot) and has only one equipped.
                    if(currentItemLeft == null) {
                        currentItemLeft = currentItemRight;
                        currentItemLeft.SetActive(true);
                        currentItemRight = null;
                    } else { //if player tries to change current weapon to a same weapon (same slot) and has both hands full.
                        tempSlot = currentItemLeft;
                        currentItemLeft = currentItemRight;
                        currentItemRight = tempSlot;
                    }
                }
                switchRightHandItem = false;

            } else if(!switchRightHandItem) {
                if(inventorySlots.IndexOf(currentItemLeft) != index) {
                    if(currentItemRight == null) { //if there is nothing on the right hand
                        if(currentItemLeft != null) {
                            currentItemLeft.SetActive(false);
                        }
                        inventorySlots[index].SetActive(true);
                        setCurrentItemLeft(inventorySlots[index]);
                        invGui.ChangeHighlight(currentItemLeft);
                        currentItemLeft.GetComponent<Rigidbody> ().useGravity = false;
                        foreach (BoxCollider col in currentItemLeft.GetComponentsInChildren<BoxCollider>()) {
                            col.enabled = false;
                        }
                    } else {
                        if(inventorySlots.IndexOf(currentItemRight) != index) {
                            if(currentItemLeft != null) {
                                currentItemLeft.SetActive(false);
                            }
                            inventorySlots[index].SetActive(true);
                            setCurrentItemLeft(inventorySlots[index]);
                            invGui.ChangeHighlight(currentItemLeft);
                            currentItemLeft.GetComponent<Rigidbody> ().useGravity = false;
                            foreach (BoxCollider col in currentItemLeft.GetComponentsInChildren<BoxCollider>()) {
                                col.enabled = false;
                            }
                        } else {
                            tempSlot = currentItemLeft;
                            currentItemLeft = currentItemRight;
                            currentItemRight = tempSlot;
                        }
                    }
                } else { //if player tries to change current weapon to a same weapon (same slot) and has only one equipped.
                    if(currentItemRight == null) {
                        currentItemRight = currentItemLeft;
                        currentItemRight.SetActive(true);
                        currentItemLeft = null;
                    } else { //if player tries to change current weapon to a same weapon (same slot) and has both hands full.
                        tempSlot = currentItemLeft;
                        currentItemLeft = currentItemRight;
                        currentItemRight = tempSlot;
                    }
                }
                switchRightHandItem = true;
            }
        }
    }