For price point .. 50mm F1.8 is a must hv lens . .
It is light, it is reasonable sharp, and offer great bokeh, and great low light photography.
If you are willing to spend a bit more, and not worry about FF camera, the 17-55 F2.8IS is a great all around lens, big aperture, sharp, great colour, (basically L lens standard, but Canon is not going to call their APS lens "L") and it is very good price too, and still offer great bokeh, and very effective IS function. (Can easy to do 1/5 - 1/10 second on landscape) That is one great lens for both scenary and portrait.
If you shoot landscape, rarely need blurry backgound, however, that is personal preference, I do use F1.2 and 1.4 for scenary once a while.
Another good all in one lens, is the 17-85 IS .. however, on the other hand, nothing is outstanding from that lens as well, but it is low price, good range, and very "fair" picture quality.
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