I'll share what I have and what I use them for. Most of us have acquired lenses that reflect what we shoot so what works for me may not be ideal for you.
1. Canon 17-40mm F4L. This is my basic working lens because it goes from fairly wide angle to "normal" and lets me include groups, landscape or full-body portraits without having to switch lenses.
2. Canon 50mm F1.8. It's fast; it's inexpensive; it's sharp. I use it for head & shoulder portraits primarily or single element portraits (one person or one dog).
3. Sigma 70-200mm F2.8. This is my action lens and I use it for taking shots of dogs moving, wildlife (although it's not quite long enough for birds or "real" wildlife) and other shots where I need both reach and speed. It's also fairly light which makes it easy to work with for long periods of time and pretty sharp stopped down to F8 or F11.
4. Sigma 28-70mm F2.8. A good all around working lens with more speed (but less sharpness) than the Canon 17-40. It's my primary backup lens.
5. Sigma 28-80 F3.5-4 Macro. I use it for macro shots primarily. It came for free with an old Canon film camera and it takes pretty decent macro images so I've kept it.

If I did a lot of landscape work, I'd want a prime (non-zoom) real wide angle lens in the 10mm to 15mm range and if I did more wildlife in the wild, I'd love either a very long prime (300mm or 400mm) or a good long zoom from the Canon L series.

Hope that helps a bit,

Jim