Some keyboard warriors swear by Alps switches, which I talked about a few weeks back. These switches are no longer manufactured by Alps Electric, so people are forced to find used switches and salvage them. There's an attractive alternative, though. A Canadian company called Matias manufactures Alps-style switches to this very day. They have many of the same properties as classic Alps along with some modern niceties.
If you want to build a keyboard with Alps switches right now, you'll have to find used switches that are at least 15-20 years old. Many of the most sought-after Alps were produced in the 1980s, so those switches might be upward of 30 years old by now. With such old components, it's hard to know how heavily they were used. In addition, Alps were only rated for about 10 million lifetime presses, much lower than modern switches. That's where Matias switches come in. These switches have a refined mechanism that's good for 50 million presses, and you can buy them brand new from Matias.
Matias switches have the same footprint and pin layout as Alps, so they work in any PCB that accepts Alps. The stem is also the traditional Alps rectangle, so Alps keycaps fit on Matias switches without any modification. Unlike the original Alps, Matias switches account for LED lighting on keyboards. The housing is transparent, so underlighting can shine through to the keycaps. The shape of the housing is the same as classic Alps, though, so it's easy to open them up even after they've been mounted in a board. These switches aren't as complicated as the original Alps, but they're close to the newer switches Alps Electric started making in the late 90s.
Matias makes switches in the three main categories of linear, tactile, and clicky. The clicky and tactile have their peak force near the top of the press, followed by a consistently lighter feel until the switch bottoms out. So, Matias switches "fall through" like Alps. This won't appeal to everyone, but it makes the actuation (right after the peak force) feel very precise. The linear versions behave more like other linear switches, with a peak force a little north of 50 grams.
The tactile and linear Matias switches are actually known as "Quiet Click and "Quiet Linear." These switches have a similar silencing mechanism to what you'll find in the new Zilent switches. A small rubber insert is embedded on the left and right side of the stem. So, as you press the switch, the rubber bumper hits the bottom of the switch housing, and when you release, the other end of the bumper hits the top of the housing. This feature eliminates much of the noise associated with each press in a way that doesn't reduce switch travel by any appreciable amount.
Matias sells a few boards pre-built with its switches, but you can also get a bag of the switches for DIY projects. A 200-switch bundle is priced reasonably at just $50.