At night, shoot the full moon with a sniper rifle.
The moon will grow and shrink each time you shoot it.
A real virtual Easter Egg
Aim for the Helipad on top of the Vice City-News Station (on the second Island). Sometimes there is the VCN Mavrick on the Helipad. The building on the right has a hallow wall so you can go through it. The hallow part is a unrealistic looking window on the left of it. Run from one side of the heliport to the other and then jump into the hallow window. There you will see the Easter Egg with a sign on it that says Happy Easter.