You just answered your own question. The Israelis have had to deal with tunnels, and yet their fence has proven enormously successful at reducing terrorist attacks. Conclusion: Tunnelling is not nearly as effective a means of entry as being able to walk across unfenced or poorly fenced surface.
What I'd really have to ask of you at this point is if you're looking for something that's guaranteed to reduce illegal entry to zero, or something that will reduce it to far below its current level. Because in the former case, you're simply not going to find it. If the latter, then we can continue with the discussion.
We do need guest workers.
We don't need to be making guest workers out of illegals here in the country. No way Jose.
Fences don't eliminate the problem, except when they're new. It takes time to dig a tunnel, and as soon as the fence goes up, digging will start. (I'm not sure, but I think the latest tunnel we found does go under a fence).
Of course there isn't any way to reduce illegal immigration to zero. We've had that forever, and we always will. What we need to do is to get it to manageable levels. The best place to start is with a guest worker program. We had one in the past, and it worked very well. The only reason we stopped the program is because our "bleeding hearts" thought the workers were being treated poorly. Some probably were, but eliminating the program was a short-sighted solution.
If we had a legal way for the workers we need to come here, I'd be as harsh on illegals as you are. But we don't. And we do need them.