One idea could be an OC who is a skilled biotic but has a unique way of using their powers, like being able to combine biotics with technology in unexpected ways. For example, they could use biotics to enhance the functionality of a broken piece of alien tech they find in Andromeda.
One common theme is self - discovery. The original characters often find themselves in a new and strange galaxy, and they have to figure out who they are and what their place is. For example, an OC might start as a loner but learn to be part of a team.
Give your character a distinct appearance. For example, they could have unique markings on their face or body, or wear a piece of clothing or jewelry that is specific to their home world or culture. This will make them stand out visually.
I really liked 'The OC's Andromeda Adventure'. This fanfiction dives deep into the exploration side of Mass Effect Andromeda. The oc teams up with some of the well - known characters from the game. It shows their interactions in a very believable way, and as the story progresses, you see the oc grow and adapt to the challenges of the new galaxy.
One common theme is adaptation. The male OC often has to adapt to the new and strange environment of Andromeda. This could involve dealing with new alien species, different technologies, and the challenges of starting over in a new galaxy.
Overall, the story of Mass Effect Andromeda is a mixed bag. It has some exciting elements and character development, but suffers from pacing issues and inconsistent writing in parts.
There's also 'Andromeda's Hope'. This fanfiction features an OC who is a scientist. It dives deep into the scientific aspects of the Andromeda setting, like exploring new planets and understanding the Remnant technology in a unique way. The interactions between the OC and the canon characters are really well - written.
A popular Krogan OC x Mass Effect Andromeda fanfiction is 'Krogan's Hope in Andromeda'. In this story, the Krogan OC is a key figure in trying to bring peace between different warring factions in Andromeda. The author does a great job of portraying the Krogan's physical and mental characteristics. Another interesting one is 'My Krogan OC in Andromeda'. It's more of a personal account - like a diary - of the Krogan OC's experiences in Andromeda, which gives a very immersive feel to the readers.
One aspect of Mass Effect Andromeda x Halo fanfiction could be the crossover of characters. Imagine Shepard from Mass Effect meeting Master Chief from Halo. Their leadership styles are different but both are highly respected in their respective universes. In fanfiction, they could team up to face a common threat that combines the enemies from both games, like a new type of alien that uses both the Reaper and Covenant technology. This would create a really exciting and unique story.