With Heart of the Swarm, Blizzard introduced a hotkey that was instantly lauded as the worst possible shortcut for getting newer players to avoid learning how to hotkey their army. Yes, I am talking about the dreaded “Select All Army” or F2 key.
IF YOU ARE USING THIS KEY TO SELECT YOUR ARMY AND A-CLICK YOUR OPPONENT’S BASE, STOP IT NOW.
This will instantly take every single unit on the map that you are using for map control, vision, scouting, dropping, denying vision, or anything else useful and clump it up with the rest of your bulking main army – in one fell swoop completely erasing all the work you’ve done in terms of setting yourself up for map control. Do NOT use F2 like this.
However, there are two ways that you CAN use this button to great effect!
Finding that Lost Unit
We’ve all done it before. We’ve sent a Raven or Warp Prism or our Vipers somewhere on the map, and just completely forgot about them. Somehow they didn’t end up in our control groups; somehow they’re lost on the map. However, if you hit F2, and click through all the different pages of units, you’ll be able to find that unit (or group of units), CTRL+left click them, and then find them on the map again! It’s a great shortcut if you seriously can’t find a unit lost somewhere on the map.
Setting Up a Spell-Caster Control Group
You should never be using your spell-caster units for map control, vision, scouting, dropping, denying vision, etc. Therefore (assuming you messed up accidentally and your spell casters are not already correctly hotkeyed), you can very quickly hotkey your spell-casters with the same steps as above. Simply hit F2, click through the different pages of units until you find the spell-casters you are looking for, CTRL+left click them, and then set them to the correct control group. This is a quick and easy fix for when you’ve already screwed up your control groups.
So in conclusion, the F2 unit is a BAD HABIT that you shouldn’t rely on. However, it does have its uses if you’ve screwed up and lost a unit somewhere on the map or need to quickly rehotkey your spell-casters.