I'm not aware of one that supports USB & ADB, but maybe somebody else knows. I wouldn't be surprised if there was such a beast around the time of the 1st PowerMac G4 introduction, but I never saw one and it's probably not worth looking for.
You can definitely use most USB & VGA KVM switches on both Macs & PCs. I use some old IOGEAR stuff in my office server room. If you toss a USB card in your Mac and really want to use an ADB keyboard, mouse, etc., then I'd suggest picking up a Griffin Technology iMate so you can use ADB gear over USB. I've had one for years that I use with my Apple Adjustable Keyboard and it works great.
The Rebound! functions very well. I'm actively using OT/SNMP on the 9500 server so I can monitor and graph its network performance, which has some very nasty memory leaks, and the Rebound! happily reboots it about once a day when it detects it's not responding correctly anymore.