Guppies because they will look at their lovely long tails and in the bettas head they see another betta, not a guppy.
Tetras, barbs and sharks are nippy and therefore your betta may well end up with no fins left.
Gouramis because they inhabit the same are of the tank and are territorial, so they and the betta would fight.
With every betta it's a hit and miss as some will be more docile than others. Your best bet is non-nippy, non-brightly coloured/fast moving fish. Most bottom dwellers are OK, but have somewhere spare to put the betta just in case.