Booster deciding that there's never an excuse not to do the right thing and trying his absolute hardest to save Coast City.
Booster refusing to give up trying to save Barbara Gordon from the Joker,when he failed and nearly died every time because it was inevitable after all.
In his current series, the most unpalatable aspect of his portrayal in I Can't Believe It's Not The Justice League - that he'd married an old lady for her money - turned out to be something he'd made up just to see if Ted would believe it. Doubles as a bit of a Take That, since this was in the last issue of Dan Jurgens' (who created Booster) run before Keith Giffen and JM Dematteis (who wrote Superbuddies) took over.
Ho Yay: With Ted Kord/Blue Beetle. It started out as something the fans noticed by accident but eventually the writers stated intentionally because it was funny.
Motive Decay: Shortly after the mantle of Supernova is passed on to Daniel, he decides to use to play videogames without having to take breaks, since the suit alone nourishes him.
Tear Jerker: Ted Kord's funeral, where Booster was unable to speak and just broke down crying. That Booster was going back in time to rewatch it makes it even more tragic.
Booster going back in time to have more adventures with Ted. Especially when Ted tells Booster that he knows him well enough to have figured out that he was from the future, and is worried that this means they aren't "close" in the future anymore. Booster assures him that they are still "really close" and that won't ever change. Troper has something in her heart.
Woobie: Tell me you didn't want to just give him a great big hug in OMAC Project.