You need toiletries. You do not need your full-sized toiletries -- especially if you're taking inter-city flights. Aim to bring only enough shampoo, conditioner, etc. as needed. Bring sample-sized cologne if possible.

Unless you're doing a lot of camping and trekking, you're going to be in places where you can purchase toiletries. Truthfully, seeing what deodorant and toothpaste are available in other countries is fun!

If you are on prescription medication, bring these in original packaging, and plan to carry on-board. Also, make your own first aid kit with the types of over-the-counter aids you deem necessary.

Bring a Swiss army knife. Do not put it in your day pack when you're flying -- it will be confiscated.