In fact, at many conventions I've been known as the "GM with the props".
- Oversized water pistols given to commando characters and space marines.
- Elaborate little trinkets to evoke a specific feeling for a character.
- Diaries filled with hastily scrawled diagrams and barely legible handwriting.
- Show jewellery.
- First aid kits to designate the party's medic.
- Bottles of wine to depict an alcohol (or wine connoisseur).
- Toy coins to depict the use of actual currency in a game.
It's not that I don't trust the imaginations of the other players involved in a session, it's more that I find people's tactile response engages at a quicker pace and a more instinctive level. If you don't have to imagine the boring bits, you can focus on the drama and the action.
This might also stem from my background in Live Action roleplaying; costume and props certainly play a more prominent role in games of this type. But I've found that bringing props to the table adds a degree of immediacy to the events at hand, they allow new roleplayers something to focus on and opens up their creative potential, they allow veteran roleplayers a new tool for their arsenal.
Some games include a props within their coded mechanisms, the first instance to come to my mind is the dagger used in the game Mist Robed Gate (here or here), but there are a few others.
But you can explore the use of props on so many levels within the context of roleplaying. They are a great way to keep track of who possesses which important items in the game.
As an example...
The most impressive prop I ever used in a game was at a convention held on the Kensington campus of the University of New South Wales, it was the mid to late 1990s. We had an unused 12 story building at our disposal, with working elevators. So we made the elevators into a system of portals and defined each level of the building as a different alternate reality. The majority of the game occurred on the ground floor (with 20 odd players), while certain groups would be sent up and down the building when they went off to explore other parts of the setting. It became easy to determine who was where in the game because different players would physically be on different floors of the building. Of course a prop of this magnitude requires a few GMs to handle properly.
I'd love to hear about props other people have used in interesting ways.