Gwencelot

Gwencelot is the het ship between Gwen and Lancelot from the BBC Merlin and Once Upon A Time fandoms.

Once Upon A Time
Guinevere was married to King Arthur, but he started neglecting her in his search for the missing part of Excalibur. On her birthday, Guinevere was alone until Lancelot came and danced with her. A villager announced Arthur had made a gift for Guinevere, but Guinevere later realized it was actually Lancelot who had prepared the gift. She thanked Lancelot for the gift.

Shortly afterwards, Arthur arrived and had figured out the missing part of Excalibur, the Dark One's Dagger, was only a day's ride away. Lancelot volunteered to go, but Arthur insisted that he would look for the Dagger himself while Lancelot stayed to protect Guinevere.

Later that night, Guinevere entered Merlin's tower and found a magic gauntlet that revealed that the Dark One's Dagger's location was Arthur's biggest weakness. Guinevere intended to get the dagger herself, but Lancelot came with her. Guinevere took the gauntlet, which lead the two to the Dark One's Vault. After entering the Vault, Guinevere saved Lancelot from the Darkness, and kissed him in relief of not losing him. She quickly apologized, saying that would not happen again. The two found the dagger, but it was protected by a magic barrier. Rumplestiltskin, the Dark One, appeared and offered Guinevere enchanted sand that gave the illusion that broken things were whole in exchange for the gaunlet. Lancelot begged Guinevere not to accept the deal, but she did so anyway.

After returning to Camelot, the two went on separate paths. Lancelot left Camelot while Guinevere attempted to use the sand on Excalibur. She eventually came clean to Arthur and told him to make a choice between her and his quest or she would follow her heart. Believing this meant Guinevere would go off with Lancelot, Arthur used the sand to make Camelot seem whole.

Lancelot eventually returned to Camelot, although he was not known to cross paths with Guinevere again. It is unknown if the sand's effects wore off Guinevere following Arthur's death and if she and Lancelot ever met again.

Fanon
This pairing has some popularity.

Fandom
FAN FICTION
 * Gwen/Lancelot (Merlin) tag on FanFiction.Net
 * Guinevere/Lancelot (OUAT) tag on FanFiction.Net
 * Gwen/Lancelot (Merlin) tag on FanFiction.Net
 * Guinevere/Lancelot (OUAT) tag on FanFiction.Net

WIKI