Definitely Commander Shepard from Mass Effect. He/She is the central character in Mass Effect and would be a natural fit to interact with XCOM forces. Also, XCOM's Central Officer or top - ranking soldiers could be prominent. They could be the ones making decisions on how to deal with Mass Effect threats or form alliances.
Well, for Mass Effect, aside from Shepard, Garrus Vakarian could be a great addition to the 'xcom mass effect crossover fanfic'. His combat skills and loyalty would make him a valuable ally for XCOM. In XCOM, the Engineers could be important characters. Their ability to understand and work with advanced technology could play a crucial role in dealing with Mass Effect's high - tech universe. And of course, any fanfic might also introduce new original characters that bridge the gap between the two universes, which could add a fresh perspective to the story.
In this type of fanfic, Shepard is an obvious choice as mentioned. But also characters like Liara T'Soni from Mass Effect could be involved. Her knowledge of Prothean technology and ancient civilizations could be useful in the context of a crossover. From XCOM, the Psi - Ops characters might be featured often. Their psychic abilities could be a unique element when combined with Mass Effect's biotics, and they could be key players in battles or diplomatic situations.
Shepard from Mass Effect is a very likely character. Given their leadership skills and experience in dealing with various alien threats, they would be a natural fit in a crossover. They could potentially lead XCOM forces or at least be a key figure in coordinating between the two universes.
Liara is frequently featured in 'mass effect crossover fanfic'. Her knowledge of Prothean technology and her overall intelligence can be used in various crossovers. For example, in a cross - over with a more magical - based science - fiction universe, her understanding of ancient technology could be a bridge between the two worlds. Another popular character is Tali. Her skills as an engineer and her relationship with Shepard make her a natural choice for fanfic authors to include in crossovers.
Shepard from Mass Effect could be a main character. They could lead the XCOM forces in a joint mission against a common enemy. Their leadership skills would be very useful in coordinating the two very different groups.
The Doom Slayer and Commander Shepard are likely to be paired. They are both iconic heroes in their respective universes. Shepard is a strategic leader, while the Doom Slayer is a force of pure destruction. Their interactions could lead to some really interesting storylines.
Well, in 'xcom mass effect crossover fanfic', perhaps a cool concept is the interaction of the characters. Imagine Commander Shepard teaming up with XCOM operatives. They could share their combat strategies and knowledge. Also, the idea of using Mass Effect's biotics in XCOM missions or having XCOM's psi - ops in the Mass Effect universe could add a whole new layer of excitement to the story.
The Marker in Dead Space is also likely to be a key element in a crossover fanfic. It has such a powerful and mysterious presence in the Dead Space universe. In a crossover with a horror - mystery series, the Marker could be the source of all the strange happenings, and characters from both universes would have to figure out how to deal with it or stop its influence.
Garrus Vakarian might also be a common character. His relationship with Tali in the original games means that in a crossover, their dynamic can be explored further. He could be involved in protecting Tali or working with her in a new situation that the crossover creates.
Master Chief from Halo is an obvious choice. His super - soldier skills and stoic nature would be really interesting to see in the Mass Effect universe. Another one could be Commander Shepard from Mass Effect. Putting Shepard in the middle of a Halo - style conflict would be exciting. And Cortana, the AI from Halo, could also play a major role. Her intelligence and relationship with Master Chief could be explored in new ways when combined with the Mass Effect elements.
Another aspect could be the exploration of the political and cultural differences between the two universes. XCOM is mainly focused on Earth defense, while Mass Effect has a complex galactic political system. A fanfiction could explore how the two groups interact when it comes to things like trade, alliances, and dealing with common threats. For instance, how would the XCOM Council (if there was one in the crossover) deal with the Citadel Council's decisions and vice versa?
One idea could be having the XCOM soldiers use their combat skills in the Mass Effect universe. Maybe they are sent to help fight against the Reapers. They could introduce their unique tactics and weaponry to the Mass Effect races.