Definately the Watctower study! First of all, we had to take an hour at home to study as a family so we would know the answers on Sunday. Then after the Public Talk, the Watchtower study was so damn long, especially when you realized that after song and prayer the Sunday meeting was actually and 2 and a HALF hours long, not just 2. Plus there was no relief in sight because we'd just have to have another meeting after that so that we could spend another couple of hours out in Sunday Field Service (which all good little elders' sons were required to participate in, unless we were taking the speaker out to lunch). The only hope was to end up in the same car group with someone relatively cool.
Not to mention that the Watchtower studies were just plain uninteresting to say the least. All those types and anti-types and modern-day fulfillments and me thinking "Who comes up with this crap?"