What was the weirdest/funniest bug that happened during betatesting?
The time during 2.2 testing when we discovered that the grappling hook was causing problems. Basically, there was 1 hook, that was modified mapside for PdH to have a longer throw and longer rope. The problem was that your client would remember the throw length from whatever map you joined the server with, causing people to be unable to throw the ropes up to the top of the cliff on PdH, or more hilariously, to throw the short ropes miles on other maps.
This was extra hilarious, because the server would take a second or so to work it out, so you would throw the short rope a short distance, people could get on it, and then the server would correct the throw to a far throw, causing mass teleportations.
This is why the grappling hooks are no longer on Giarabub (as shown in the 2.15 trailer).