It all started during the beginning of our second term (winter term) with one guy on my floor taking a shower and another filling up his recycling bin with ice and cold water and then dumping it on the former. Thus became the tradition known on our floor as "nuking". Soon we were all filling up our recycling bins with cold water and randomly walking into each other's rooms and pouring frozen hell onto each other (none of us ever locke dour doors because we trusted each other enough not to, plus it always was a hassle to lock and unlock our doors) regardless of whether the victim was sleeping, studying, playing games, working on their laptop, or in a few cases, fucking their girlfriends. This eventually escalated from filling up recycling bins to just buying a lot of water guns and water balloons. Again, this was during winter. Our dorm floors were constantly soaked and our shared washroom was constantly wet. We had to start buying toilet paper/stealing it from other floors because ours were always wet (try as you might, you can't really clean your ass with cheap, wet, 1 ply toilet paper). Our RA had an idea of what we were up to, and she booked us a few times. We came up with the dumbest lies, but she was stressed with her own shit that she was just like "fuck it" (we later found out she was put on suicide watch during that time). As exam season came around, our floor of about 15 guys became divided into 3 factions and we were in all out war. By the end, one of the guys broke into the utility closet and grabbed the water hose and just sprayed us all down Scarface style as we ran into the washroom trying to evade each other. We then decided that he was the winner of our war and that we should probably start focusing on our final exams. When a few of us came back for the Summer term, they found out our entire dorm house (3 floors) was closed down and undergoing treatment to clean up all the mould they found during their post-term inspection.
tl;dr we had epic water fights and gave our dorm house lots and lots of mould.