Interesting question. My 2p worth...
Things I wish I had done more of on my ppl training:
Actual short field/soft field
More short solo x-c as confidence builder
Circle to alternate runway stuff as above
Go/no go weather analysis
Dead reckoning
'mission based' training - eg deliver an aircraft for maintenance and collect it as a solo navex - forcing trip to possibly more difficult/challenging destination, not joining 'by rote' to a regular x-c destination.
Things I was lucky to do and would recommend:
Train in a few different countries
Go foreign - my first long dual x-c blackbushe schipol
Do an actual IMC trip
Fly into big airports (APCH-TWR-GND-ATIS) as well as uncontrolled
Do some longer x-c