I'm with NGI, which isn't cheap but there's no throttling and has extremely fast responses, although it's only 2Mbit in downstream. It's one of the best for gaming, though, and fairly reliable, and with excellent technical assistance (although I can't say the same about the same about administrative assistance). You must pay in advance, minimum contract 3 months.
The best offers are, in my opinion, those of Telecom Italia (
www.187.it) since Telecom owns almost totally the phone lines in Italy. This means that every single tech assistance request on ADSL, if it involves the lines, has to be passed to their technicians. Telecom doesn't apply throttling and it's quite stable. Not the fastest response, anyway. Help phone lines are a disaster. The contract can last less than a year, but in that case you must pay €40 to end the contract (in case of the 7 Megabit offer at 19.95 a month plus €3 a month to rent a router from them).
These are the two ADSL providers I used at home, so I can only talk about them. There could be cheaper alternatives (such as Tele2), but I can't say if they're reliable or not since I have no personal experience with them, except for knowing that Tele2 applied throttling but had to give up because of angry customers. But things can change very quickly and tech assistance can be a nightmare with every provider, and that's why I went with a provider which has serious contractual guarantees.
Fastweb could be a nice alternative too, but it doesn't assign public IP addresses normally (only by request and it's not cheap), so you have to stick with all the limits of its architecture (no access to the PC's IP ports, except from the Fastweb network). Most people are fine, but I wouldn't be.
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