Regardless of brand of generator, I'd recommend an oil evac pump, full synthetic oil (splash lubrication is really hard on oil, so might as well use the best out there), spark plug wrench, replacement spark plug, and one of the more important things:
Bring plenty of fuel. Sometimes I've gone out on a weekend with the generator's tank full, and three (five gallon) gas cans that were full. Came back with empties, mainly because it was extremely hot/humid. Other times, I just needed a little bit of gasoline because I was running the generator to charge the batteries.