[radhakr]

Being easily able to spawn whatever vehicle I want is good, preferably able to spawn at least a couple as well.
Trials made of lots of objects are fun, like on Awesome Stuntages.
Being able to get around fast - lots of teleports, ability to create a temporary teleport for myself (I've only ever seen this on one server that wasn't mine, it's great if you're trying to pull off a stunt and need to start over).

More generally and more importantly, you need a good bug-free script, decent admins and good information (help, etc).