One hack I always thought would be fun is to set it up where one person’s computer would start getting 78 nanoseconds slower than the time beacon at random intervals, not enough of a difference to be noticeable at first but over time that computer would slowly get out of sync with everybody else.
Their game play would lag – just a little – nanoseconds are small – but nanoseconds becomes microseconds become milliseconds, etc and things that depend on time (internet applications mostly) would just start getting odd little glitches now and again