Funnels are pretty basic items. I've got a few with openings of different sizes to fit narrow-necked bottles and to fit larger jars, but the new canning funnel from Progressive ($15) has a few features that make it worth the storage space it takes in my kitchen.
First, it's designed specifically for canning jars, and fits securely on both regular and wide mouth jars.
Second, because of the design, it can't tilt or wobble. Well, I guess it could, if you put a couple of shims under it. But otherwise it's very stable, and that's a big deal. Most of the other funnels I own tend to tip - at least a little bit. When I'm trying to fill hot jars with hot food, it's nice to know that the funnel isn't going to move around.