.com of course
Leaving the joke aside - all TLDs (gTLDs, ccTLDs and even newTLDs) have the potential to be "hot". You just need to get the right ones.
I own domains in lots of TLDs and there is demand for all of them.
If you want my advice don't go into the numerology stuff until you get some experience and you can say you got a "feel" for the market.
No matter how many new TLDs are coming out always remember .com should be the priority =-D
Aside from the king though I am noticing some really nice trends for .tv and .cc domains. Any TLDs that are not .com my focus has always been to go for the one word or short keyword terms. These are the ones with most values in other TLDs.