Water temp and oil pressure gauges.
Ok, I was heading to a local speed shop near me yesterday after work to get a gauge there in my slant 6 and all of a sudden it wouldn't stay running and then died. I tried the spare balast resistor but no go. I called AAA and they picked it up and brought it home. It was too hot to sit in a parking lot and play with it. Easier to work on it at home. On a side note, after I called AAA I heard that old familiar sound of an ice cream truck so I flagged him down and got a milkshake to cool me off while waiting for the tow.