How can I disable mobile data completely? I have a pre-paid plan and don't want to use my mobile data except for two days in the year. However, since there's the quick option button mobile data, I fear I might press the wrong button when I'm dizzy.

So is it possible to deactivate mobile data completely, such that a press on the "mobile data" quick button won't activate it anymore? Or a little bit more drastic: how can I remove that feature from my phone?

If the solution is device specific, I'm looking for an answer for a Samsung Galaxy S2 (GT-I9100, running stock 4.1.2), but I would like a general solution.
Create a dummy APN and select that as default.

With this, even if you enable data accidentally via toggles, it would still not connect.

 PS: Added as an answer as suggested by OP