Move permanent ink on a pack of gum!
Imagine this: you borrow a pack of gum from your spectator. You (or the spectator) draw a big bold X on one of the compartments. You then take this pack of gum, and with no cover at all, cause that mark to visibly jump to another compartment. One by one, it travels across the whole pack, to end up on the top. You then give the pack back to your spectator, and they can examine it as long and as thorough as they wish; they won't find anything.
Key points to remember:
•Use a borrowed pack of gum
•Easy to do
•No angle restrictions
•Use any brand of blister packaged gum
•Gimmick is easy to construct (and we provide plenty of the necessary material)
•Explained in great detail in multiple camera angles