In a break with tradition here, I am going to recommend a company rather than a particular object. This is because, taken individually many garden lights look incredibly boring. But it’s what you do with them that counts. This site not only has a huge range of uplighters, downlighters, deck lights and rope lights but it also has a comprehensive section explaining what to do with them all. This page is particularly useful www.moonlightdesign.co.uk/acatalog/lighting_effects.htm especially if you are starting out from a position of no lighting at all out there.
Good garden lighting won’t be cheap but it can create really magical effects and turn your garden into something special so do consider carefully what you are trying to do before you spend any money. Just as you take care where you place your lamps indoors so you should in the garden.