For shooting landscapes, any prime lens will perform excellently on the 5Dm2, L or no-L.
For shooting everything else, there's basically three groupings:
1) The cheapies, being the 135/2.8, the 50/1.8, the 35/2, the 28/2.8 and the 24/2.8. These are great, but have loud autofocuses and aren't comparatively fast. They are tiny and inexpensive, though, and (so long as you're not too concerned about bokeh) all have totally powerful optics, easily outperforming any zoom.
2) The mid-range, being the 100/2, the 85/1.8, the 50/1.4, the 28/1.8, and the 20/2.8. These autofocus silently, quickly, and in general have nicer build qualities, but on the flip side they halate wide open and are known for chromatic aberrations. However, shooting to avoid those situations, they take stunning photos.
3) The high range, being any L prime. These all provide knock-your-socks-off performance wide open, and as such are the best things out there for photographing anything involving people. Their only issue is that stopping them down beyond f/4-ish (depending on which lens) actually hurts image quality, so as a solution, don't stop them down
Hopefully this helps! I've actually used about 80% of Canon's primes, so these observations are based mostly on my own experiences.