The basic four are: Chef's; petty or parer; bread; and slicer.
There are exceptions to all the rules. Let an honest assessment of your own skill levels, the likelihood of their improvement, and your own taste guide you. At the end of the day, it's always and always should be personal choice.
Learn to be a proficient sharpener, and acquire a decent sharpening set so you can do it. Sharpening isn't everything, but whatever's in second place is way behind.
Most pros with decent knife skills prefer a chef's in the 10" range. You don't see many using santokus, and of those few, most are women. It's an easy knife to use, but not very productive. Chef's knife come in two basic shapes, German and French. Japanese made chef's knives -- sometimes called gyuto -- are usually French profile. The German profile is more powerful and a little more intuitive. The French profile is more agile and rewards good skills. Japanese made knives use different alloys from those made in the west, and can be made sharper and will stay sharper longer.
Sharp trumps weight for almost every purpose, and the very strong modern trend for cooks with good skills is to Japanese made chef's knives
A petty is a long paring knife -- 6" is the common length. It can be used for all paring functions, boning, and just about anything a 10" chef's is too long or clumsy for. The typical paring knife shape is the same as a slicers, so a 6" petty functions as a small slicer, too. It's very useful for trimming proteins.
A bread knife is useful for all sorts of pastry, and the serrations will even go through partly frozen food. You don't necessarily need one right away, but it will help protect the edge on your chef's.
A chef's knife is NOT a slicer. A slicer is far more useful for trimming and portioning.
For a lot of reasons Shun are not very good for the money, and doubly so regarding their chef's. They do feel good in the store, but the universe is filled with better knives.
- How are you going to sharpen?
- What's your price range?
- What's your skill level? By that I mean do you pinch and claw? How long does it take you to cut a no. 1 pan of mirepoix? Can you cut Brunoise? Do you sharpen a knife well enough so that it will cut Brunoise through an entire shift without "mincing" or bruising the veg? Can you break a chicken in less than three minutes? All those things as opposed to "pretty good."
Your post implies that you'll be learning with your new knife, rather than playing it like a Strad the day it arrives. Deduction doesn't count for much, it's important to know.