Safari uses Cmd-Shift-{ and Cmd-Shift-} to switch between tabs, as does Xcode. However, you can change them to whatever you like by selecting Preferences->Key Bindings and searching for "tab"
I've done that, and unfortunately attempting to switch those to ctrl+tab and ctrl+shift+tab instead changes them to cmd+ctrl+tab and cmd+ctrl+shift+tab with no way to not use the command button.