There was some debate as to whether this one should really qualify for the list ("Are they actually kissing? Are they both male?") but in the absence of other options to choose from we really had no choice but to include Dreamcast's bizzare virtual fish tank.
Even if they're not kissing, the fish are definitely swapping fluids of some kind via their dangly bits. And, while we don't claim to be experts in identifying fish gender, both the canoodling fish look like males to us.