Bard! How to troll your friends!
It's simple! Just wait till they're using their long CD ult and BAM save the enemy team with your ult. Trolltastic!
Example? Your kat E'd into the enemy team and ulted? Well not anymore! Give that enemy team a free Hourglass! Go on... do it!
For bonus points team up with Kalista and have her give her spear to someone other than you. Then when they try to commit to a fight, BAM pull them back as soon as they've used their cooldowns! Example- Wukong ulted? Well best pull him back in the middle of that!