Jumping rope, allright. I've never liked this since a very young kid, I just can't keep the rope rotating

. Do you guys think that just jumping without the rope would work the same ?
Not at all. Your arms and legs will get out of sync without noticing and the more tired will lax - without the tripping to indicate that you're dropping intensity!
I'd suggest burpees myself.

What you might want to try is just running on the spot, but with each step you have to lift your knee up so it's waist height (minimum thigh parallel to ground) - surprisingly tiring and gets a sweat on quickly!