samples of parametric equations

[xyz3003]

I need samples of parametric equations:
x=Fx(t);
y=Fy(t);

the samples must be useful or famous in math, physics or engineer, not be created randomly meaningless.

one that I know is to describle ellipse:
x=A*cos(t);
y=B*sin(t);

I need 2 or more good samples for my report.

thanks.

found so far:

Cycloid
Epicycloid
Hypocycloid
Hypotrochoid
Spirograph

[nicktacik]

A cycloid is a good example. Look it up.

[xyz3003]

nicktacik,
thanks.
by your clue, i found a set of them:

Cycloid
Epicycloid
Hypocycloid
Hypotrochoid

I add them in my post and will use them soon.

Any other interesting locus?