Nuclear energy is already a viable option -- if done properly (the Navy has been using it safely for over 50 years).
Coal, oil will be the primary source through at least the next 50+ years, unquestionably (unless certain circle's attempt to sabotage it are successful).
Nuclear fusion as others have noted is certainly the holy grail of energy, but I'd doubtful we'll see anything viable in the next 50 years, though you never know.
Hydroelectric is viable on a limited scale, and always can be.
Geothermal, same as hydro, limited scale, serious technological difficulties.
Solar, same as hydro, but much more limited scale, though of broader use on very small scales. Will always be relatively very expensive inasmuch as the panels don't last but 5 - 10 years max.
Chuck Norris slowly munching on a banana? Obviously better than wind power, but at his age, how long can we rely on him to save us? Personally, I think bovine flatulence (not on the list, unfortunately) is more viable though.