Metal or glass, though glass is probably a safer bet. The metal used in sex toys is typically medical-grade stainless steel, so it's just as safe, if not safer, than glass; it's hypo-allergenic and immune to chipping, which is something that can happen to cheaper glass toys if they're mishandled.

Silicone is another good bet. Some people prefer the hardness of metal or glass; other people prefer something softer, like silicone.

Another interesting choice is stone. There are a few companies making sex toys from polished granite, which is like metal or glass but heavier; I've talked to women who really like the weight of stone. Expect to spend a lot more for those toys, though; granite is a very difficult material to work with, so granite toys can get pretty spendy.

best bets are silicone - it should advertise: pure silicone or something like that - and glass.
and buy good lube too. nothing with sugar in it. 

@Man@mancouch - 

@reckless_eagle@xanga - 

@Rebel@mancouch - 

Why, boys, you really know a lot about dildos!!!

Do NOT buy jelly if you're sensitive! If you want something a little softer, high quallity silicone should be fine also.

I would think granite could be a bit porous. Even though it isn't supposed to be. As some have offered, silicone would be a good bet. I saw one brand out of Norway or Sweden or Denmark that had the best quality silicone, and they were very well made. Can't recall the brand, but you can find it on Amazon.

wow I didn't know guys knew so much about dildos. Yea silicone. Or anything that doesn't vibrate. I hate that shit. lol
This picture is stupid, it's almost touching the ribs. lmao. I seriously hope it's a photoshop.