Who wins?
Saying "Uno" vs Calling Uno on someone
Saying "Uno" wins 53% to 47%. 118 more put them in the same row. From Board Game Rule Debates Tier List. Pick a side.
RandomPossum on Saying "Uno": it's printed in the rules, two card penalty if you forget
soggy_frog on Calling Uno on someone: catch them before the next player goes and they draw two
Board Game Rule Debates Tier List: the full ranking