I only had a couple.

Last year at Leeds The Tears vs. The Go! Team (I chose The Tears cause I love Suede and never saw them live)
Also Pixies vs. Kasabian (although no real contest there, as Pixies are the greatest band ever)
Bloc Party vs. Echo & The Bunnymen (again the legend won)
Razorlight vs. Hot Hot Heat (went for HHH)

That's it, no real toothaches here. Still it's worth having a bit of dilemma at a festival, I still got to see more than anytime before ever. (I live in Poland you see :))

Any of you remember any clashes?