No matter how hard you try, I can open what you can't. If it wasn't for me, on your front porch you would stand. What am I?
A key.
Why this works
This riddle plays on the dual meanings of "open" and the concept of access. A key literally opens locks that you, without it, cannot unlock, hence "I can open what you can't." The second part hints at a scenario where, without a key, you would be stuck outside your home on the porch, emphasizing the key's importance in granting entry. It cleverly highlights the reliance on a simple object that has a significant role in our daily lives.