In close up magic most often coins are changed for other coins. It's so common that we have a word for that particular effect: Spellbound. But the minds of the magicians don't seem to stray very far from it. Sometimes the coins change into rings and keys. Sometimes little balls change color....
Method: You will need ONE real steel ball and the other ones are cocktail tomatoes treated with silver edible spray paint. That way all you need to do is to show how real the real steel ball is, switch it for a tomato and eat it.
Mentalism: Think about mentalism when it comes to spellbound. A regular key can be visually changed into a bent key. A fresh leaf could become an old, dry leave, which in presentation could be a "changing season" thing or in mentalism could be a "sucking out the aura" thing. Two magnets; if you switch one from something that looks similar both will no longer attract each other. Ergo "sucking out magnetism" could be the effect. (Where does the magnetism go? Maybe a demonstration of PK-effects is in order. The falling block of wood makes sense now!)
Changing the Effect: A broken monocle could repair itself.... you see stuff has not to become other stuff. The effect could be perceived differently. In this case a restoration. Now think even further. Some that gets repaired could also just go back in time to a point where it wasn't broken. Now if you think about changing an old toy into a working, shiny version of the toy... you are on the road to create a memorable, emotional effect. As it refers to so many aspects of any body's childhood. When wonders where still acceptable!
Go bold with the plot: What if it is not just the objects that changes, but the whole universe? What if a pack of salt in this universe is a pack of sugar in the other universe? What other changes might occur? I hope you can see where I'm going with this. I swear if I hear the King Midas story again I will leave the room. Changing stuff to gold is a great trick, but don't go back to plots that have seen better days.
Changing parts of nothing: Have you ever done the Spellbound Move with "nothing"? You could see something in the air and catch it. Show the "nothing" between your fingers and then mention the fact that the audience probably won't see it. The simple reason. They are seeing the wrong side. "It's a hole, but you are looking from the inside out. That's why you don't see the edge. Let's me twist it around a bit!" Then add the palmed steel ring to the picture in a twisting motion, as if you have turned a hole inside out.
This is a stupid premise and will not believed by the audience, but they will play along as long as they are entertained. And I think that this premise is a bit of a mind twister. One that is entertaining. (Of course you could continue with the steel ring. It's a portable hole after all. But what's one the other side of the hole? I hope you can see that this flies off in many directions!)
So you close up guys. I hope you put your coins and balls to rest for a while and experiment with other little objects that have the right size for manipulation. Such as: finger rings,
bunched up silks,
blocks of wood,
small light bulbs,
blocks of glass,
One more effect that is easy and cool.
Effect: "Have you ever seen MacGyver? I love this guy. He can build the most complicated stuff from simple stuff." You get out a box of matches "All he needed was a box of matches. He would take just a few of them." A few matches are taken and the box is put away. "And a rubberband. He would wrap the rubberband around the matches and then add a paperclip."
Method: A rubberband is taken and wrapped tightly around the matches, so they become -sleight of hand-able. Then a paperclip is taken as well as a palmed minibomb (basically just a small black ball with a piece of flash string attached) the paperclip is slipped under the ruberband as well, and then a Boboswitch is made. One hand assumingly holds the match-rubberband-paperclip bundle, but in fact that hand holds the bomb. The other hand goes in the pocket getting a lighter and ditching the bundle.
"That is how you make a small bomb which can take out two, may three blocks."
Then the fuse is lit. "Damn, a dud!"