I think a better question would have been: "what are your favourite mentalism effects". As has been said, this all comes down to personal choice..and of course, where you will be performing, and for whom.
I agree with Bill Abbott's "Celebrity Smart Ass", Cody Fisher's "Confabulation"....I also really like Jason Palter's "Red Carpet". These are all stage or parlour routines.
For close-up, you simply can't beat "Ultracinese" for sheer impact as a PK effect. And I agree with "Psypher" as probably the best/easiest imp device, though Ali Noura's "Steam" is staggering if you routine it correctly.
It's true that this is a vast field, and really difficult to make any suggestions other than the effects I personally use and perform.
My favourite "magician fooler" is "Nostradamus' Chest", and I also enjoy loads of multiple-out solutions, as these can be the most powerful of all.
Kollossal Killer has been mentioned several times.
;)

http://www.youtube.com/watch?v=UwGboVduTS4
I think as a spectatot, this effect will be so amazing.

I would suggest psycokinetic silverware and Liquid metal. They're classics I know, but in all of mentalism I feel pk and metal bending effects thee most powerful for spectators.

Presentation is everything!

Just to say, I'm a sorta newbie, well one year in, and these two are great for me, You can use Psypher in your own way(this is the first thing I atcally ever put into a routine which I came up with) And Cataclysm is a total killer, use it along with a wallet such as infinity with many outs and also with the BIP book and you have a solid routine!