Palindrome Check: which edge cases did you miss first?

Palindrome Check looks like a five-minute problem, and then the edge cases show up.

Which one caught you on your first Submit?

• upper and lower case
• spaces and punctuation
• the empty string, or a single character
• something I have not thought of

Also: do you compare the string to its reverse, or walk two pointers in from both ends? Which do you find easier to get right, and why?