I hope I'm not boring y'all with the gardening talk, but I've waited so long for spring to finally get here, I just can't help myself.
My current philosophy for plants is that they need to multitask. Good looks ain't enough. You gotta bring something more to the table. In Show Biz, they talk about a triple threat; In baseball, they talk about a five-tools guy; even cooking geek Alton Brown preaches against uni-taskers. Who doesn't love a beautiful rose or a flowering cherry or crabapple? But why not plant the tree that will give you both the flowers and the fruit? Why not plant the rose that will give you edible and/or medicinal rose hips? If you don't fancy eating rose hips (I'll admit I never have), maybe they'll attract some new and interesting wildlife.
So what are some of the possibilities? For me, producing something edible is huge. Attracting wildlife is a nice benefit, especially if that wildlife will benefit you as well, by say, keeping the insect population down. Producing something useful is a plus too, like bamboo, or even quality lumber if you expand your horizons a bit. Trees are good for more than just lumber though. Their roots penetrate deep into the soil, which can draw nutrients and trace minerals up to the surface. When the leaves fall in autumn, they provide some of those nutrients, and lots of organic matter, to help improve your soil (well, unless you bag 'em up and ship 'em off to a landfill). Well placed trees can keep you cool in summer and let the sun shine in during winter. They can slow down the cold winter winds. They take gobs of carbon dioxide out of the air, and put out gobs of oxygen back in. They cut down on erosion. They can even cut down on pollution. Some, like willows, can take up enough water from the soil to lower the water table if you have excess moisture. Others, like locusts and redbuds (a personal favorite) can take nitrogen out of the air and add it to your soil, to share with other nearby plants. But that trick isn't limited to trees. In fact, most people know of this effect from growing legumes in the garden, like beans and peas. Even big corporate farmers have figured out that if you rotate corn and soybeans, you won't have to dump quite as much chemical fertilizer on the ground.
You can even set up symbiotic relationships, or "communities" of mutually beneficial plants. The classic example is the "Three Sisters." Native Americans used to plant corn, beans, and squash together. Tall growing corn provides a trellis for the beans to climb, while the beans add nitrogen to the soil, and the squash give some much-needed shade at ground level, keeping everybody's roots cool and cutting down on moisture evaporation. And all three produce food. For more examples like this, just look up permaculture. They have some pretty cool tricks.
Given the right circumstances, even something as mundane as grass can be turned into meat, dairy products, and wool, via grazing animals. Heck, you can even take it a step further and get some pulling power or transportation out of them if you pick the right grazers.
In case you're wondering, I grew up in suburbia, playing computer games, mowing lawns, working fast food jobs, and trying to blend in. Now I find that I've morphed into some kind of nerdy redneck hippie who writes too much...
It's much more fun this way though.