A large group of plants with new varieties being made available all the time.  Commonly known as the "house leak"  they can be found in the alpines section of most garden centres.  They range in size from around a cm up to over 30cm, with green, red, blue, and many other colours available.  Finally leaves can be smooth, hairy with some varieties even having a web of fibers covering the whole plan. 
 
Often plants sold in garden centres as "un-named" or "mixed varieties", and given hybrids and the number of forms it is almost impossible to name these. Bigger or more specialised sellers will sell name varieties and this is where the gems are to be found.  The flowers are dramatic, with the plant dying after flowering,  although by then most have formed clumps and the young plants will quickly fill the gap left by the dead rosette