Interesting indeed!
First user controlled mechanical device not being a flipper? - Cowpoke, 1965?
First last chance ball saver on drain? - Goldeneye, 1995 (beats WOZ)
First saucer to saucer juggling? - Fastbreak, 1997?
First head-to-head game? - Fastbreak, 1997?
These may not be earliest, but should at least give something to try and beat!