For marking the blades, it is hard to beat a stencil and etcher. Lasers aren't really the right tool unless you want to spend big bucks. Dollar for dollar, lasers are poor economy.
For custom handle artwork and faux-scrimshaw, a laser is great. They are very good for woodworking projects and doing artwork on wood and other softer materials.
On my list for sometime soon is a 100W CO2 laser setup. It will cost what a good grinder costs. If it didn't have other uses besides knife projects,. I wouldn't even consider one.
For those who haven't been around laser engravers, they require a fair bit of ancillary equipment, are not at all "plug-and-play", and have consumables.
Don't think that the cheap 40W things on eBay will work for knife work. Don't think that you will open the box, plug it in, sit down, and engrave a knife blade.