What are your most favorite scenes in you favorite Alien film?

1. Eggmorphing scene.

2. Alien looks at Jonesy.

3. Derelict, outside and inside.

1. Space Jockey

2. Kane Facehugged

3. Ripley going back to stop self destruct

1. Alien- First glimpse of the Derelict- nothing else like it at the time.

2. Alien Finding the Space Jockey

3. Aliens- Finding the Queen

For me it's a tough choice because Alien has such great scenes.

• The opening scene where you are slowly toured through the Nostromo and the crew wakes up from hypersleep.

• The chestburster scene where the crew is joyfully eating and then the Xenomorph bursts out.

• Ash attacking Ripley and gets his head knocked off by Parker.

The franchise has lots of memorable scenes. It is difficult to distill it down to just three- but those are the terms of the OP. 

Ya that's why I limited them to 3 because I can go on for paragraphs about great scenes.