Are you saying you want to get every bit of the kernel, including the somewhat woody tip cap, which attaches the rest of the kernel to the cob? We don't really think that's what you're saying. No one wants to eat the tip cap.
So what you're really asking (we believe) is, "how can I remove most of the kernel without crushing the guts out of it?"
Most people would tell you to hold the cob straight up over a tray and use a very sharp knife to cut through the kernels about three-quarters of the way from the top of the kernel to the cob. That's great for the two rows of kernels you're cutting. What most of those people don't address, though, is the fact that the cob is curved, and if you're cutting straight through two rows of corn, you're also slicing through the neighboring rows on either side at an angle and spilling their guts all over the place.
There are mandoline-like gadgets that do the same thing, and some of them are scalloped in an effort to account for the cob's roundness. There are one-piece corn slicers, that absolutely take the roundness into account, but not necessarily the variation in thickenss of the cob. All work to a greater or lesser degree - with some, you wind up with more usable kernels and less "creamed corn." In cases where there are similar products on the market, some work really well, while knock-off products may be terrible.
The product we've recently found that we think works best is the corn zipper, which shears off two rows at a time and not much else. It doesn't take into account very well variations in row width or rows that aren't straight. It's a little challenging to get the depth right, as well, but with a little practice, you should be able to peel off row after row of corn - either before or after cooking. Going two rows at a time is slower than using the whole cob tools, but that may be a price worth paying for more intact kernels.