5. Susan Foreman
The Doctor's grand-daughter. Susan travelled with the First Doctor, Ian and Barbara, meeting Daleks, Aztecs and many more alien creatures and historical figures. Susan was the first companion to cease travelling with the Doctor, but it wasn't entirely her choice. When they land in the 22nd Century, they TARDIS crew is shocked to find the Daleks have invaded Earth.
They work together with the rebelling population to stop the Dalek's plans and reclaim the planet. While doing this Susan grows close to a man named David. The Doctor sees their connection and locks Susan out of the TARDIS at the end of the adventure, delivering an emotional speech about how he will miss her. The Doctor then takes off, leaving Susan to have a settled life with David.
This boy genius travelled with the Fourth Doctor and, later, the Fifth Doctor. An arrogant, selfish child at times, Adric is definitely not one of my favourite companions. However, in his final story, Earthshock, he finally begins to grow on me. He risks his life to save Planet Earth when a space freighter hijacked by Cybermen is on collision course with the planet.
A time jump causes the freighter to travel back to 65 million years ago, still on collision course with Earth. Adric is about to unlock the navigation controls when a dying Cyberman shoots at him, misses and hits the controls, destroying them. Adric, with no time to escape, dies in the collision with Earth while the Doctor, Tegan and Nyssa watch, unable to help, from the TARDIS.
3. Donna Noble
Donna first met the Tenth Doctor when she materialised inside his TARDIS on her wedding day. On the same day, she met aliens, found out her fiancé was in league with the aliens, and watched her fiancé be killed by aliens. Needless to say, she turned down the opportunity of space travel, but soon regretted it and hunted down the Doctor again.
Facing Sontarans, Giant Wasps and the shady Vashta Nerada, Donna's last stand came up against the Davros and the Daleks. When Donna touched the Doctor's severed hand, she formed a Time Lord-Human Metacrisis. However, her human brain couldn't handle this for long, so the Doctor had to wipe all trace of himself from Donna's memories, and if she remembered, her mind would burn up. This left the Doctor, Donna and her family distraught.
2. Rose Tyler
Rose was the first companion of the new series and the Doctor's first companion after the end of the Time War, in which he lost his home planet. Rose stuck by him when he regenerated into his tenth body and they even had a hint of romantic tension. Rose was willing to sacrifice her family to stay with the Doctor, but it didn't happen that way...
Rose elected to stay in her world with the Doctor while her family travelled to a parallel world to be safe from being pulled into the Void. Covered in Void Stuff and being pulled in to the Void, Rose did her best to hold on, but when the lever slipped, she reached out to fix it. This resulted in her being pulled towards the Void, but her father used a dimension jump to save her and take her to the parallel world just in time, leaving her trapped with no way of seeing the Doctor ever again. Well, not quite ever...
1. Amy Pond & Rory Williams
Amy and Rory spent a long time travelling with the Eleventh Doctor and experienced many things with him, such as marriage, the birth of their child, the breakdown of their marriage, their reunification and their eventual fate. They battled Daleks, Cybermen, the Silence, and Silurians, but a last stand against the Weeping Angels led to the end of the Ponds' journey through time and space.
Travelling to present day New York, Rory is touched by an angel, causing Amy and the Doctor to pursue in the TARDIS, meeting River along the way. Reunited with Rory, Amy, River and the Doctor change the course of time several times, before returning to present day New York in a graveyard, where Rory noticed a gravestone with his name on. Intrigued, he stops to look and is touched by another angel. Unable to return to get him, Amy sacrifices travelling with the Doctor in favour of being touched by the angel to be with Rory.