Tee hee. Nearly everything I plant self seeds and spreads itself like mad! You don't say if you want annual or perennial plants. In my experience perennials are much less likely to self seed than annuals. Here are one or two that I have that are relatively well-behaved.
1. Madagascar periwinkle - Catharanthus roseus. Comes in a variety of colors apart from roseus.
2. Zinnia - Zinnia elegans ( not Z.haageanus as this self seeds). Wide range of colors. This is an annual.
3. Venus slipper - Calceolaria hybrids.
4. Antirrhinum - Antirrhinum majus and hybrids. Will self seed but easily controlable. Biennial.
5.Four o'clock flower - Mirabilis jalapa. This goes under a variety of names, but as the one I have given suggests it doesn't open till late , so needs a W facing position. Perennial.
6. Salvia ( Sage) - many different species, incl. the culinary one, though this is not so showy.
7. Lavender - Lavandula - many diff. species,flowers not so showy, but good for toning down the more violent colors and of course the scent.
8. Dahlia. It's a good idea to lift the tubers occasionally and enrich the soil.
9. Bulbine fruticosa. S African bulb. Forms neat clumps, not invasive. Orange and lemon.

10. Coneflower (Echinacea purpurata) and Rudbeckia, both USA natives. Taller plants good for the back of the border.

Hope you have fun growing some of these.