Fuseli created one of the most recognizable paintings of the Romanticist movement: the above featured The Nightmare. It's a famous piece, or rather one version of it, that neatly sums up the whole of Romanticism on one canvas. Fuseli, of course, created many memorable works, though none that have reached the level of cultural ubiquity that The Nightmare has (though that could also be said of many great artists' complete portfolios). His influence was vast, affecting such geniuses as Blake.
Thor, in the boat of Hymir, battering the Midgard Serpent
The Night-Hag Visiting the Lapland Witches
The Shepherd's Dream