Whilst not a terribly committed or skilled gardener, I am the proud owner of a lemon tree and a grapefruit tree.
The lemon tree is a Meyer's lemon, which is a cross between a lemon and a mandarin orange. Squeeze one into a glass of fizzy water and I get instant, delicious, naturally sweet lemonade. Lovely!
Don't like feckin grapefruit though, which is a shame, especially as the bugger has a bumper crop this year.... but it does provide the perfect shady spot in our little courtyard, so I can't complain.
I also have a few cacti ("barrell" cactus and some giant Brazilian thing which is almost as tall as the house now), a splendid Tombstone Rose which covers our outdoor bar :icon_cool :icon_wink and four big, shady pine trees. The Mrs deals with the other, more girly stuff (hibiscus, geraniums, wystiria, philodendrons, jasmine, etc)