I don't carry these with me, but I perform them in succession if I really want to freak someone out.

OOTW(using only about a third of the deck)
ID
PSYCHIC STOP
DEEP ASTONISHMENT

While these may seem like obvious choices, they are for a reason. I know of no other mentalism effects that are so clean. With these effects, there's just no logical way out.

While Deep Astonishment is a great effect, it isn't mentalism. Nor do I consider it "clean." Just my opinion.

Bill

A pen and a piece of paper means to be always prepared to do a magic square.

Christian

DA can be a great mentalism effect! And while it may not be 'clean', the shock at the end can cause enough misdirection to clean everything up.

The loop

I hereby abstain from any further debate but DA is mental magic at best.

Bill

Paper, mechanical pencil/pen set, NW, peek wallet.

+ / -
T.Trans
C Tear
and if conditions allow
MOAB

Xpert
Predicta

I only have my, knowledge ,experience and personna with me. If I have to do anything in promptu, then I can find soem pebbles for Kurotsuke, a deck of cards or at least a piece of paper and a pen which I can go on an immediate show. And bending spoons and forks are always a jaw dropper.The only thing I need to be on my mood to do something.

Out of Body - Larry Becker. It's terrific.

My wallet is always ready for Kenton's Kollossal Killer and it's always on me....and it's always a killer.

Neil Tobin's Xpert.
I just got it, but it will have it's place in my pockets permanently.
Sven

A swami gimmick, my huge inflated ego, and my own horn,

which I toot as frequently as possible. I guess

these are pretty standard props.

Pad for the PCT
Gel Pen
Mind Controller wallet
Head with info about the magician's choice looking for three objects to use.
and a NW

That may change next week

SUC containing - blank cards, Busche's 21st Century Peek cards. and a pre-bent 10p with finger prints embedded in it.

A deck of cards, either stacked in OBCS or a stack I don't remember the name of
Some Post-It notes to post predictions onto the spectator's forehead.
Some business cards.
Sheets of paper and pen to do mnemonics

You can do a lot of great things WITHOUT any real props, like giving a reading, hypnosis, mnemonics,...

SUC with my bussiness cards to do Kentonism.

Blank cards to use with the SUC and to do Ian Rowland’s NMDD.

My fortunetelling cards

A lion claw, just in case...

Gandalf's own cast-the-evil-wizard from you spell (LOT II).
With OBCS standing by,

An impromptu book test (either through the use of the centre tear, or by forcing the page) always gets a very positive reaction.

Also, I agree with an earlier post about the strength of doing a magic square. Performed quickly and accurately people really enjoy these - I know many people who have kept the squares that I have created for them.