My cat has been messing with that insects. It looks quite unusual.
Anybody here can help me identify it, so I can make sure it's not dangerous?
The overall appearance fits well with the subfamily Lamiinae (flat-faced longhorns). I would also guess it's in the Batocerini tribe. Though I don't think this is your species, per se, here is an image of a female Batocera rufomaculata with white stripe for comparison:
Once you provide more information about location I can give you a more precise answer.
Monochamus scutellatus is almost certainly incorrect. Notice the lighter coloration , wider body shape, and presence of a lateral white stripe along the side of the OP's insect vs that of M. scutellatus.
I think that your insect is a White-spotted sawyer. For more information check this: Monochamus scutellatus, commonly known as the white-spotted sawyer or spruce sawyer,is a common wood-boring beetle found throughout North America. Adults are large-bodied and black, with very long antennae; in males, they can be up to twice the body length, but in females they are only slightly longer than body length. Both sexes have a white spot on the base of the wings, and may have white spots covering the wings. Both males and females also have a spine on the side of the prothorax. Most research done on M. scutellatus focuses on their relationship with burned forests and the logging industry,with interest also being shown in their mating behaviours.