The first soft-politico stickers I saw all over cons in the 90s/00s were their 'FUCK MICROSOFT' and 'FUCK GATES' stickers that exploded after the MS/Linux/SCO conflicts.
Before the MS debacles (was there a before?) it was mostly FREE KEVIN everywhere.
..which for reasons lead to 'this machine hacks oligarchies', and 'piss: it's whats for dinner' stickers shown in the link.
Speaking on that : Woodie Guthrie was better at marketing slogans than himself -- kind of interesting to consider how many more people are familiar with the 'This machine...' than his music.
When I was going to these things I tended to avoid 'extreme' ones -- I was often job hunting and didn't need to project an image that may hinder that effort.