For small areas, ceramic heaters are very good. They’re safe, and most brands shut off when tipped over. They’re also (relatively) cool to the touch.
For larger areas, a good quality oil filled radiator heater is effective. An even larger area could require a second one, but usually not.
Whatever you choose, especially the radiator, just give it time to heat the place up. They won’t heat up a room instantly, they need time to work.
(P.S. I sell them.)