Necessities in your bag

Tide Pen for when the groom drops a piece of pepperoni on his shirt.

Needle and white and black thread for the groomsman that didn't check his shirt at the store and finds that the sleeve is split from cuff to elbow. 

And like Bob said, a lint roller. I got one from Walmart where they keep all the travel sized stuff so it's pretty small. 

I may have to go and get the portable steamer.  We've been talking about getting one for about a year now. 

Wow, Susie must take her purse!  Just kidding.

I take along a crescent wrench, pliers, my Leatherman Wave  , a roll of duct tape, and a 2 1/4 lb sledge (in case they give me headaches!).

Oh, and I bring along my Digital Photography for Dummies book just in case I have time to do a little light reading!

Travis

The problem is no matter how much extra stuff you carry with you they will always need something you don't have.  Sometimes just knowing where to get something is good enough.  The split sleeve mention above actually happened, but I didn't have a needle and thread with me at the time.  I suggested they call downstairs because the front desk probably had what they needed or at least could point them in the right direction.  5 minutes later a guy from the front desk was at the door with a needle and white thread and I still got bonus points from the client and groomsmen. 

I do have a little sewing kit in my wedding bag now though.

Lots of good comments and information from you wedding guys...

What about you nature shooters?

What about you guys that shoot location portraits and or models

What about you landscape only guys

When I'm out for nature/birds I always carry
Water, Energy bar, gps, binoculars (8x 42mm), Mike: I carry a Leatherman Charge.

Mike, Marian, Anton??

Always with me:

sewing kit, safety pins, variety of clamps, gaffer tape, pen and paper, model and property release, pen light, batteries, measuring tape, camera and flash manuals, cleaning supplies

Location portraits:

umbrellas (variety), remnant cotton material (~6-8 yds) of varying colors, MaryKay blotting sheets, small 1st aid kit, water for everyone

Outdoors and Nature (depends on time of year and length of trip):

-in the pack; matches, 1st aid, pocket knife, GPS, compass and maps, rain suit, various game calls, 2-way radio, hand warmers and gloves, bug spray, extra socks, jacket/coat, bedroll, sunblock, firestarter, knife sharpener, book on edible plants, plastic bags, various food items and water
-in the vehicle; shovel, blankets, extra shoes, extra change of clothes, toolbags, chains, cell phone, tow strap, atlas, and a 72-hr kit.

My outdoor excursions are typically a little more than an afternoon drive, in case you were wondering.

Travis

Oh, it hurts! Trust me!

Bob, you should keep chicken cutlets handy for that kind of thing. No, not the fowl variety, lol, but the silicone breast enhancers that look like chicken cutlets.