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—actually, make that five—unique features that make it worth the storage space it takes up 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.
Third, it's got a collar that makes it impossible to spill food onto the rim of the jar, even if you splash or spill food outside the funnel. If you've done any canning, you know that it's important that the rim of the jar is clean before you put the lid on. Sure, you could still drip goo onto the jar when you're removing the funnel, but that's not the funnel's fault.
Fourth, the collar lets the funnel stand upright rather than rocking and rolling around when you set it down on a flat surface. Not the biggest innovation in the world, but it's a bit less messy, and it means that the parts of the funnel that actually contact the food are not going be cross-contaminated by anything else that happens to be on your countertops.
And fifth (and best!) it's got measurements on the collar of the funnel that shows headspace. If you've ever done canning, you know that jars are supposed to be filled to a specific level based on the recipe. If you do a lot of canning, you might be able to eyeball those measurements. Well, not me. I like the visual crutch.
If you already own sixteen funnels, maybe you don't need an extra one, but if you're thinking about doing some canning and need a funnel, this is an ideal choice. This funnel is also available in a set with two other canning tools, if you happen to need them.
There's also an all-plastic funnel in a similar design for a lower price. But since I haven't seen the plastic funnel, I honestly don't know if there are other differences that might be significant.
Disclaimer: Testing samples were provided to Serious Eats.