Video game related, Deckard cameo seen in the Blade Runner PC game if one triggers the right event. I freaked out as a Blade Runner fan.
Also video game related, the ghost of Jordan Weisman, one of the co-creators of Shadowrun occasionally appearing in the Seamstress Union bar to chat; for Kickstarter backer copies of Shadowrun Returns. I love when games do little things like that.
Cringe cameo's are almost anytime a big celebrity makes an appearance on a TV series. I shouldn't say 'anytime'. Some of the time it works out, but most of the time it's the TV cast awkwardly pandering to a big celebrity and it's just.... yuck. Arrested Development had a lot of really well done celebrity cameos.