Definitely outdated & user-unfriendly interfaces.

Although many new games are guilty of that too.

Boot disks. "Ain't nobody got time fo' dat!" (Dreamweb is a bitch to run)

Manuals. Or games requiring the manual to play (looking at you flight and space sims!). Can't find my copies of X-Wing and XvT. Maybe I sold them, but I know I won't be installing the GOG versions till I print the manuals.

Switching between disks and discs. Loading, then not reading the disk properly, reloading, etc. (Wing Commander III and Blade Runner, anyone?)

Idiotic DRM that works against paying customers (damn you Scarface and Runaway 2). Some times I'd use a no-CD patch...

You really don't need much more than the reference card cheat sheets to play. Those were created for good reasons. ;)

Yeah, I should have been more specific about what I'll be printing. Unless I manage to find my aforementioned copies (if I haven't sold them, that is).