The 4e skill list is very functional, and there are some great ideas for tying it to powers, but sometimes you just want to stretch the bounds of what a skill can do, or as a GM you want to create challenges that might be a little bit more creative than just using skills by the numbers. For folks in that situation, I present the following list that I started pulling together when I was trying to write some non-typical skill challenges.
Unexpected Things Skills May Be Useful For
Acrobatics - Catching spilled drinks, making a dramatic entrance, dancing with style.
Arcana - Droning on and on and on, make fake magic look authentic, repairing old magical widgets.
Athletics - Flexing of muscles or otherwise generally putting on a show, dancing without embarrassing yourself
Bluff - Sincere sounding compliments, pretending you've met someone before.
Diplomacy - Insult someone without them being able to call you on it, say the right thing about someone's outfit.
Dungeoneering - Find exits, talk about architecture.
Endurance - Look attentive through intensely boring conversations, drink all night.
Heal - Discuss hangover cures, spot a limp.
History - Recognize someone's name, explain politics.
Insight - Read the subtext of a work of art, judge who is really important in a room.
Intimidate - Exude subtle menace, make someone angry, escalate to a superior
Nature - Cook, get along with someone's dog.
Perception - Judge the quality of someone's clothes, spot a cheater.
Religion - Give a sermon, discuss philosophy at great length.
Stealth - Escape a conversation, cut into a line.
Streetwise - Know the odds on a horse race, know who's on an invitation list.
Thievery - Entertain small children, repair small knick-knacks, slip something into someone's drink.
Feel free to add your own!