Dried corn is usually avoided as it can develop fungus that can kill your rat. Fresh and ground corn are just fine.
I would stay away from Jigglers since its basically sugar and gelatin. If you have to give fatty or sugary foods make sure small amounts and there might be some nutritional content. ANYONE who has rats with tumours, watch the sugar carefully as it can feed the tumour and make it grow even faster.
T-man, peanuts have a lot of oil and fat, but are fine in moderation, cooked sweet potato (not the green bits) are much loved and very healthy for your rats and small amounts of dark chocolate can be given during times of respiratory distress (its a bronchodialator).
Watch the protein intake, moderate is fine, and chicken bones are also much loved by rats (watch your fingers tho!
). Don't worry about them splintering like with a dog since a dog crunches thru them and a rat gnaws...no chance of splintering.
Ask Shrek if he likes them...
(Fostered a biter boy about to be euth'd, took him in, socialized him and reintro'd to his ladylove...all in 2 weeks...miss him so much.
Here's a list of Forbidden Foods, etc that a lot of ratowners go by...its a bit outdated but its got some good basic info.