Just the common household torch does fine for most stuff.
Something like the WT2301 is what I use, the TS1500 would be nice too I guess. The self ignite feature and an adjustment knob is key. I can still turn the knob for on/off of the gas flow but the auto off would be nice, I just didn't want to spend $60 for the feature.
http://prograde.espacecommunications.com/subcat.html?id=1
Even the generic knock off's work fine it doesn't need to be a name brand but ya get what ya pay for.
Uh, yup.
MAP gas is the stuff if you need more heat.
Now you ain't gonna do a 10x12" 1/2" thick piece of steel with it, but pretty much anything you see here on these forums except for some of the larger knives