I'm going to keep posting this in every single thread of this type I find. Unfortunately for you, the best magic is in books.
I posted this before, and it's always the same.
Here's an idea. Look for them yourself, find the ones that work for yourself, and make them "hard hitting"! In all honestly, looking for the shortcut by asking for "best of" effects isn't gonna do you any favours, and 95% of the time will not get you the most hard-hitting effects you can perform. That's right, asking for good tricks will actually, the majority of the time, get you tricks that, when performed by you, will be second rate and extremely common. So you'll be performing the same old stuff and probably not as well as you could be.
Rather than ask "Where can I find the best effect", ask "Where can I find effects (possibly of x plot or from x magician)", go out, look through everything, and find what works for you. You want average material, ask for "good" DVDs. And if you're satisfied with decent, go ahead. Some people are happy with being decent, and that's fine. But if you want to be better than that, with the best material and the highest possible impact? You'll have to work harder than that.
The main reason for this is that the strongest effect in my arsenal, in all honestly, would probably not work at all for you. This is due to many reasons - personality, presentation, and just the effect in general. Many, many people for example list Stigmata as their strongest effect, and many people buy it. You wanna know the truth, 95% of people's presentation of Stigmata is ****. Stigmata could be so, so much more. I'd bet my money that half the people who've said Stigmata in this thread can't present it to save their lives, and could easily improve their own performances. But no, they rely on the effect, rather than relying on themselves as a performer, and this separates the chaff from the wheat.
If you really want strong effects, you need to tell us what you're interested in, specifically, a plot or an author. Then you need to go look at everything by that author or on that plot, and decide what works for you, use that knowledge to mix the effects together, and base a presentation on what appeals to you, not what appeals to us. My favourite effect happens to be Zamiel's Rose, and yet I barely know anyone who has the personality to pull it off, so I never suggest it, it would be a travesty, the epitome of ruining magic. I mean what do you want me to say - follow your instructions exactly, and give you an effect that won't suit you and you won't be able to make the most of? I'd rather say this, the truth.
This is not to say we (or I) don't want to help. This is to say, rather, that it should be the right help, if you really want the best magic. Far more important to getting good reactions is to know what to perform, but when and where. Once you master this you won't need to ask about best tricks.
Go buy a book or something, that's where the good stuff is. Since you said "Unless" they're very good, here are some books which are VERY good from memory - all of these are better than 99% of the DVDs out there:
Inner Card Trilogy
Mnemonica
52 Memories
The Magic of Ascanio
Drawing Room Deceptions
Jennings '67
Book of Secrets
Books of Wonder
Card Control
Expert Card Technique
The Art of Magic
Card Manipulations
