zb3D Grapher
This little tool can graph implicit 3d equations, parametric surfaces and parametric curves. This means you can also plot implicit 2d equations, 2d function graphs, 3d surface plots etc. Summing up, this is a powerful toy ;)
Note = sign in an implicit equation doesn't really mean =, it means "goes through", but that shouldn't be a problem. I haven't heard about any grapher that could plot "(x^2+y^2+z^2-16)^2=0"
This uses THREE.js, mathquill (desmos branch) and marching cubes to draw implicit surfaces. I had to write "math parser" on my own, so if something doesn't work, its probably my parser as it is the most buggy thing ever. Of course you will need a WebGL capable browser, I recommend firefox. You can use latex commands in an equation box like "nthroot", "sqrt" etc. To navigate through blocks use arrow keys.
Use mouse to control the camera, left click + drag to rotate, right click + drag to pan and middle click + drag to zoom.

Graph type:
Equation: ax^2+by^2+cz^2-d = 0
x = f(z, t) = csinzcost
y = f(z, t) = csinzsint
z = f(z, t) = ccosz
x = f(t) = cost
y = f(t) = sint
z = f(t) = t

a:   b:
c:   d:

z from to
t from to

z, t quality: , values per graph

t from to

t quality: values per graph

Box for:
Box for:
x from to
y from to
z from to

x, y, z quality: , , values per graph

Convert to: coordinates