I can start with:
- forget to remove control lock
- leave the trim set for landing before take-off
- not pushing mixture rich before takeoff at sea level if you taxi with very lean mixture
- in a Cessna, not putting the fuel selector to "both"
Control lock, you'd also have to forget to box the controls sometime before takeoff.
Trim set for landing is unlikely to cause a crash - In many planes it's very close to the takeoff setting, in others you're never going to break ground with that trim setting.
If you taxi with a very lean mixture, the engine should die when you push the throttle in for takeoff. If it doesn't, you're not leaning enough.
Now, all those things should be on the checklist, but the flip side is...
I generally operate with the mentality that everything on the pre-flight checklist is there because it's killed someone in the past. I think there are very few items on there that haven't.
...there are far TOO MANY items on most checklists. Some of them have killed people. Others are there to appease lawyers. Others are because manufacturers of single-engine pistons make the checklist into the entire instructions for flying. For the record, there are more checklist items before takeoff on the Cessna 172 than there are on the Hawker 800.
My favorite example of this is the following, from the C172 preflight checklist:
Master Switch ............ ON
Fuel Gauges .......... CHECK
Master Switch ........... OFF
The master switch items should not be on the checklist. Fuel gauges should be. And if you check the fuel gauges and they say empty even though you saw fuel in the tanks, maybe you should realized that the gauges are electric and the master is off without having to add two extraneous checklist items to make up for lacking systems knowledge! Or, this could be on the before start checklist right after you turn the master on for good.
These extraneous items result in the checklists being printed in tiny print, which has likely killed people because it's too easy to skip over an important item on the checklist by accident.
I really wish GA checklists were done better.