I love rhododendrons. Gladioli I can't quite cope with in the big loud flower stakes, but rhodos need make no apologies for themselves. They come in so many vivid colours, the more clashing the better, and they really do look like they're made of some wondrous tissue stuff. These purple ones though, seem to be the prototype, how they revert when they naturalise ( and yes, I know they're a menace when they do that, acidifying the soil etc).
Azaleas are pretty good too, especially the yellow ones that have a perfume like ylang-ylang.