The Doctor has offered you one of three things for your birthday. A Sonic Screw Driver, a piece of Psychic Paper, or a makeshift Perception Filter that you can wear around your neck. You can only choose one of these things.
Advantages: Psychic interface, you just point and think. It can even emit various frequencies that can temporarily stun most people and animals. Essentially it's a magic wand
Disadvantage: Has limited battery life and you're not getting another one when it dies out.
Advantages: Like the screwdriver this has a psychic interface. Show it to anyone and they see what you want them to see. Letter of recommendation from the president of the United States, backstage passes to your favorite concerts, CVS discount card, anything.
Disadvantages: If it's too big a lie, or you're not confident enough, or the person you're showing it happens to be one of those rare geniuses who can't be fooled by psychic paper, you could into a lot of trouble.
Advantages: It looks like an ordinary piece of jewelry, but it gives off natural vibes that cause a person to avoid looking directly at you or noticing you're there.
Disadvantage: Cannot fool cameras or security equipment. Also, like with the psychic paper, there are some people who can resist the filter and will notice you even if you're just in their perhiphery.