Great idea!!!
Love it!
*prepares his magic mugs for some funny spells
But also this spells could be used in a offensive way as Seytra said, but in wars and stuff...
For example:
Guild A is at war with Guild B. Guild B is loosing, so it\'s members decide to cast some fireworks, fog, and the bouncing spell, it would cause lag, some members of Guild A would be frighten and would cause the members of Guild A to bounce arround, guiving advantage to the Guild B, by attacking at a long distance either with spells or other ranged weapons avoiding the lag caused in the area where Guild A is.
Another use of this spells could be a little usefull, but without being a combat/defensive spell, like turning something into another, levitation (as someone said already), change the color of something (mmm... don\'t like my black megara... maybe I\'ll make it blue).
A (usefull but non-combat) powerfull spell could be casting a huge cloud that would start to rain, you know for the fields in bad times to farmers... things like that...
Anyway, I would love to see players all wet because they were fighting with balloons, people without some clothes on, a pink Enki, etc... Because as Irish-Wiskey said, this things make the world alive and less boring.