At this point, there are no known nuclear powered jet engines.Anyone, of course, with better information, is welcome to refine this answer.Both prototype nuclear powered jet engines ever built are stored in the EBR-1 site parking lot in Idaho and can be seen by anyone when they tour the EBR-1 reactor historical monument and museum.
The ONLY nuclear device(s) ever used in a world war was the Hiroshima & Nagasaki atomic bombs that were dropped in August of 1945, ending WWII. Nuclear powered naval ships were used in a number of other conflicts, but not nuclear weapons.
Nuclear-powered aircraft were researched in the mid-20th century, but none were ever successfully developed or used. The main challenges included safety concerns, weight of the reactor, and potential radiation exposure to crew and passengers. The idea has largely been abandoned due to these challenges and the focus has shifted to other forms of propulsion for aircraft.
Steam
Ummm, yes the cars in your imagination are powered by milkshakes!
horses
The Westland Wasp is a turbine powered, shipboard anti-submarine helicopter. Also a unique first generation jet helicopter made famous for being the first helicopter ever to be operated from (frigates and destroyers) and the first helicopter to disable an enemy vessel at sea. Is a naval vessel used for kits and landing in difficult areas
no.
No
On a missile? No, the only nuclear weapons ever used in war were the 2 aerial bombs dropped by B-29 bombers on Japan to end WW2. All the nuclear tipped missiles ever launched with live warheads were tests, either air defense missiles or high altitude effects shots.
Maybe Chernobyl, but only for a short time. Ever heard of SL1? Both are sad events. There are some very large coal powered plants in the USA and the rival the nuclear plants.
Depends on if you are talking about military or civilian and what "strongest" means to you.