I have a bunch of true Flexcut whittling knives, which are purpose-built for whittling. Most are fixed blade knives in various shapes, and all have a grind around 30 degrees inclusive. One of them is a Flexcut Carvin' Jack, which is a folder that has multiple blades, all designed for carving. It is a nice knife, with curved blades, gouges, v-cut blades, etc.
You really want as flat a grind as possible for whittling, and the edge should be polished to glide through wood.
I do, however, prefer taking the "backwoods country boy" approach to whittling, where you take whatever knife you have in your pocket out and start whittling. For that I prefer a more traditional knife, and one you can use for multiple uses (like cutting up an apple).
My favorite whittler has become the now hard to find GEC courthouse whittler. It has a main wharncliffe blade with secondary pen and coping blades. The wharncliffe blade on this is perfect for whittling due to the long and pointy shape. I sharpen all the blades on this knife to 30 degrees using a Sharpmaker, and I hone them until they shave hair off my arm.
Here it is on a classic ball-in-cage carving I made, with the beginning of a wooden chain behind it.
Keep in mind that I usually take months to whittle a project, as it is not something I do with purpose, but something I do to relax and unwind, so a project like this will use many knives, as I like to carry different knives at different times. I generally carry a multi-bladed knife, and sharpen at least one blade for general use (around 40 degrees inclusive) and at least one blade for whittling. I have several Swiss Army knives that I have done this with, usually sharpening the main spear blade at 40 degrees, and the pen blade at 30 degrees.
A stockman also makes a good whittler, and if you get the very common spey blade very sharp all the way through the radius of the tip, it comes in handy for scooping out wood.
Most of all be really careful, since when whittling you are nearly always cutting towards yourself, and a slip of the knife can lead to a nasty cut. If you are going to do a lot of whittling, use a glove on the hand you are holding the wood with, and a thumb guard on the whittling hand. Since I do a lot of impromptu whittling, I often do not have my safety measures with me, but have found that if I am slow and relaxed, and keep my knives razor sharp, I rarely have any accidents. I say rarely because I still cut myself every once in a while, so I will not recommend doing this, unless you are okay with the occasional sliced finger.