As of lately:

People who think ice is the absolute, ONLY way to win in Shatter.
People who think base capping is the only way to win in Shatter.
People who want to wait for the other teams to do something before they do anything. Tactically, that's insane.
In 24 man, half a team of healers pocketing one person/each other. Like seriously, man up.
Bots.