... my 50 mm 1.4 canon lens. Why? Because it can do this.
As in, it has such a low aperture that it can totally isolate the subject from the background and make that leaf look like it's floating.
Or just have one small point of the railing of a walking bridge in focus and the rest blur away. (those are technical terms right there)
Yup, I love this lens. Ever since the first time I used it, I was hooked. Best investment ever.