Depends. If you get creative enough, a lot of swords could be used for iai.
For instance: the cutlass, falchion, scimitar, and similar curved swords are similar enough in shape that drawing them like a katana wouldn't be unfathomable.
However, it's also possible to draw a straight sword— for instance, a shortsword or a gladius— that way. In fact, the Chinese have a style resembling iaijutsu performed with the straight-bladed jian
You could also conceivably do it with a BFS
strapped to the back, like a claymore, by pulling it away from the sheath and over one's shoulder, but that's where things get a little impractical.