Here are some apps I have on my iPhone:
HoldEm - Texas holdem poker game
Top 3 Solitaire - Has Spider, Klondike and Freecell
Cube Runner - a cool game that uses the motion of the phone to maneuver an arrow through a maze of cubes coming at you
Lightsaber - turns your phone into a lightsaber complete with motion sounds and clashing sounds
Pocketpedia - Basically Amazon for your phone and lets you keep a database for what DVDs, CDs, Games and books you own.
PocketGuitar - a guitar you can strum by touching the screen. Fun way to kill time when you are in a line or sitting somewhere bored.
Zippo Lighter - It's just cool and fun to play with a fake Zippo
Ocarina - Blow into the bottom of the phone and play this fun flute like instrument
7 Horror Books - Comes with 7 horror books: Bram Stoker's Dracula, Mary Shelley's Frankenstein, Robert Louis Stevenson's Strange Case of Dr Jekyll and Mr Hyde, H.P. Lovecraft's The Call of Cthulhu, Oscar Wilde's The Picture of Dorian Gray, Gaston Leroux's The Phantom of the Opera, Washington Irving's The Legend of Sleepy Hollow
Classics - This one comes with even more books to read and is regularly updated with new books at no extra charge: The Count of Monte Cristo, Frankenstein, 20,000 Leagues Under the Sea, Alice in Wonderland, Dracula, Robinson Crusoe, The Time Machine, Call of the Wild, The Adventures of Huckleberry Finn, The Jungle Book, Paradise Lost, Hound of the Baskervilles, Gulliver's Travels, A Christmas Carol, The Metamorphosis, Flatland, Pride and Prejudice, and Treasure Island
Labyrinth LE - A neat get the marble to the finish avoiding the obstacles game using the motion of the phone to do so. Addictive.