I'm even worse in it... sometimes I can't hold a laugh at "tragic moments" in cinema, when everyone else are silent. It happens when these "tragic moments" are too cliche or too poorly played... they just start to seems too ridiculous in such a cases, and I can't hold myself
But the most loud laugh in me cause bugs in video games... you know, for example, when mob unexpectible stuckles in textures or fall through the floor... or just the opposite, flies away, even despite it hadn't supposed to be able to fly. I can't hold chuckle, even just writing about it. It becomes the most ridiculous, if I play in team games... when especially nasty bug happens (for example, out of sync games of different players), and it cause players to fail a mission, everyone swear, but I laugh loudly and sometimes can't stop for a few minutes.
My boyfriend was somewhat annoyed by this, when we only started to communicate. Now in such a situations he just waits untill I stop laugh or laugh, too.
If talking about the comics... I very rarely laugh at them, more often just smile or chuckle a little bit. For example, this one moved me to laughter a bit: