You could argue that any trick is the best. I won't dance around it though, my favorite effect on the website is Flux and I'll explain why:
-You can do this one trick over and over again and never get caught (granted you have a good presentation).
-If you know nothing else you can still do this trick.
-You hardly need a routine and you can be well known for this one thing.
-You should learn a gimmickless way to do this trick as well just in case (look at Tequila Hustler)
-This is a reputation maker for sure. People will constantly be asking you to do it.
There are a thousand other books that would give you much more knowledge, and you'd get much better much faster. Also, I have no idea what your character is or you performing environment. Lucky for you Flux is flexible.