When I go to Tools > Options > Environment > Keyboard and
Type in Query.Sp_whoisactive
Press shortcut keys: Ctrl+F1
When I press Ctrl+F1, It still calls Help.
Click on Tools > Options. Then navigate to Environment > Keyboard > Query Shortcuts. In the stored procedure column next to Ctrl+F1, type Sp_whoisactive.
Next navigate to Tools > Options > Environment > Keyboard > Keyboard, and find the command Query.CustomSP1. Assign the shortcut Ctrl+F1. Then search for the command Help.ViewHelp and remove the mapping for Ctrl+F1 there.
In Sql Server 2012, control + F1 is assigned to View Help (Check the Help menu in SSMS). I don't think now we can re-assign to some other functionality. But still I'm not sure why the Control+F1 option is provided in Query Short cuts. So there may be a provision to re-assign this also. Not sure, we have to explore the new features in Sql Server 2012.