Hex (second row, second from the left in your image) and Torx (top row on the right) are widely used, because they are more suited for automated tools and/or are more resistant to deformation than flat-head and Philips.
The security bits(thanks to agentp for providing this paragraph) The "security" fasteners are pointlessoften used not for "security" per se, they're all readily available as you've foundbut simply to stop the mechanic from accidentally removing a screw that shouldn't be removed. Even if he has the tool, it might make him stop and think "maybe I ought to go study the procedure first". The one in the steering wheel is undoubtedly there because of the air bag, with the presumption that anyone qualified to work on the air bag can get the proper tool.
Can't help you with sizes, other than noting I found lots of Torx screws, including a Torx T25 for the rear seat backrest in an Audi A3.