Hamamelis x intermedia 'Sunburst' is perhaps one of the most floriferous yellow flowering cultivars available.
Hamamelis x intermedia 'Ruby Glow' is an old cultivar & it's flowers are not that large but it's deep red color is still something that is hard to beat.
Chimonanthus praecox 'Su Xin La Mei' This plant was imported from China by a friend under this name but it may not be a valid Cultivar name. I believe the "La Mei" part at least is just the Chinese word for Chimonanthus. Very similar to the cultivar 'Luteus'