Han Solo and a Skaven from Warhammer. Han's roguish charm and ability to get out of tough situations could be pitted against the devious and sneaky Skaven. The Skaven's underhanded tactics and Han's quick thinking would make for some really entertaining encounters as Han tries to outwit the Skaven in various situations across the two universes.
Another interesting concept is a crossover during a time of great chaos. For example, the warp rifts in Warhammer open up near a key Star Wars system. This causes all kinds of chaos as the daemons from Warhammer pour into the Star Wars universe, and the various factions in Star Wars have to figure out how to deal with these otherworldly threats. It could also explore how the Jedi might try to use the Force to combat the daemonic influence.
Definitely Luke Skywalker. He could bring his Jedi wisdom to Earth and teach people about the Force. Han Solo would also be great. His roguish charm would be fun to see on Earth. And of course, Darth Vader. His imposing presence would create a lot of drama.
Definitely Indiana Jones and Han Solo. Indiana's tenacity and knowledge of archaeology combined with Han's roguish charm and piloting skills would make for some great interactions. They could be on a quest for a valuable artifact that has significance in both the Star Wars galaxy and on Earth.
Definitely Darth Vader and Jack O'Neill. Darth Vader with his imposing presence and dark side powers would be a formidable force against the Stargate team. Jack O'Neill, with his military experience and sense of humor, would be a great contrast. Their interactions could be really intense and full of conflict.
I think Dom Santiago from Gears of War and Han Solo from Star Wars would be interesting. Dom's loyalty and Han's roguish charm could lead to some really fun and unexpected interactions. They could be on a mission together, with Dom's military skills and Han's piloting abilities complementing each other.
Perhaps an Imperial Inquisitor ends up in the Star Wars galaxy and tries to manipulate the Sith and Jedi for his own ends. He could see the Sith as a useful tool, not realizing how dangerous they truly are until it's almost too late. This could lead to a three - way battle between the Inquisitor, the Sith, and the Jedi.
One interesting plot twist could be the combination of the Force from Star Wars with the psychic powers in Warhammer 40k. Imagine a Jedi using his Force powers in the grim and dark universe of 40k, facing off against Chaos psykers. Another could be the appearance of Imperial Stormtroopers in a Warhammer 40k battle, their white armor standing out among the chaos. Maybe they could be mistaken for some sort of new xenos threat at first. And a third plot twist might be the discovery of a lost Star Wars planet in the Warhammer 40k galaxy, full of unique technology and species that both sides would be eager to control or destroy.
Charizard would also be great. It's a large, dragon - like Pokemon that could fit well into the Star Wars aesthetic. It could be a wild Pokemon that a group of rebels or stormtroopers encounter on an unexplored planet. It could either befriend them or become a formidable enemy depending on how they interact with it.
Definitely Darth Vader. His presence would create a lot of tension. He could be on a mission to hunt down the Rebels crew, and it would be a battle of wits and strength as they try to outmaneuver him.
Definitely the Lotus from Warframe. She could be like a wise advisor to the Jedi Council, sharing her knowledge of the Orokin and the Tenno. And Darth Vader would be a great addition too. Imagine the confrontation between him and a powerful Warframe like Excalibur. It would be an epic battle of light and dark powers.