This may or may not be common knowledge, I just thought of it. We know that each runner is (in theory) supposed to have a type of ice that they are good at beating with their icebreakers - Shapers have good code gate breakers, Criminals have sentries, Anarchs have barriers. But there's also a kind of ice that each runner is good at beating without icebreakers.
(At least this appears to be the original design intention from the first few sets; some abilities have since been shifted around, like Criminals leaning more on Link when originally Shapers did. That's why all my card examples are from spin cycle or earlier.)
For Anarchs, their no-icebreaker-needed type is code gates. While the most commonly played code gates are basically just like barriers with a different subtype, if you look at all the code gates that are printed and don't get played, you notice that there are a lot of positional ices - cell portal, chum, sensei, hourglass, RSVP, marker. Since Anarchs can destroy the ice behind these (or in front for cell portal) they can then ignore the code gates, killing two birds with one stone.
For Criminals, it is barriers. Criminals want to deny money to the corp, so they love running into barriers and forcing the corp to spend money rezzing them and not getting harmed for the facecheck. Then they can derez with Emergency shutdown to bleed the corp dry some more. Also, since barriers are used more on remotes than other types (where it is important to keep the runner out not just tax them), Criminals can use Inside job to simply ignore them.
For Shapers, it is sentries. A lot of sentries are tracers, and Shapers can beat the trace with their high link from Rabbit Hole / Toolbox or with their high credit pools from Magnum Opus. Other sentries do net damage or program destruction, and once again the shapers are prepared with things like Net Shield and Sacrificial Construct.
This would imply that the third type of ice would be the weakness for each runner. Anarchs were originally typecast as reckless runners which would make sentries their problem; code gates being positional and cheap encourages deep servers which criminals would have a problem with (note that crims didn't even get a decoder in core); barriers being good at keeping people out makes them a good choice for rush decks which is good against the traditionally slow shapers.