What are your pet peeves? I probably could go on for a while about mine, but I'll hone in on one specific pet peeve of mine for now:
I can't tell you how much I can get ticked off by Steam notifications. See, when I'm in a server and people are rule-breaking on mic or otherwise doing stuff I need to pay my attention to, it's really annoying when the list on the bottom right of who is currently using mic is blocked by "SomePersonINeverTalkTo is now playing Team Fortress 2." or "SomePersonIDontEvenKnow is now online." They always seem to pop up at the worst times, and the only way you can quickly click away from them quickly is to click it and thereby open a Steam chat, which makes it even more annoying IMO. And before you say it: Yes I know you can disable these notifications, though I've always wanted to keep track of this stuff for myself. Though, I've had to recently disable the "___ is now online" notifications given a bad predicament where someone was mic-spamming racism and Tuesday Steam maintenance had just ended for everyone.