Be careful of the "wallet check" too often. Pickpockets will often watch to see where men check for their wallets when they're nervous. (They may even get a partner to say something about pickpockets.)
As for the front pocket, it's harder to get at than back pockets, but there's still a "lift" that can be done. If your wearing loose, or dress pants, they can pull up the fabric inside your front pocket until its contents are reachable. They do this a little at a time, while behind you in a line, or on a subway or something. I would think it would be harder to get out a front-pocket wallet than a money clip, because the edges will catch.
Don't rely too much on believing you'll "feel" the attempt. Picking pockets is based on the theory that your brain can only focus on one physical sensation at a time. Try it -- close your eyes and cause some kind of mild pain on your leg or arm, then lightly brush another part of your body at the same time. The sensation is significantly diminished. And noise is only effective compared to the ambient background noise.
When in crowded areas, I often carry a "dummy wallet" in my back pocket, with a slim wallet in the front pocket. When traveling I use a money belt. I've heard the ones that hang around your neck work pretty well, too.
What about pickpockets and weapons? Do they go for weapons? Or do the weapons deter them?