Get Shaky, Get Better at Everything
This exercise will tax you, frustrate you, and cause you great discomfort. But most of all, it'll make you a far better lifter. Why? It involves the use of unstable or "oscillating" objects.
Lifting unstable, shaky things works to improve your motor control and stability. It also improves your intermuscular (within a muscle) and intramuscular (between different muscle groups) coordination and overall muscle function. In short, this method of training will make you better at just about anything. Here's one way to do it.
Double Javelin Press
The regular javelin press (using one bar) is good overhead pressing variation that requires a combination of strength, stability, coordination, and skill. However, many lifters cheat the system by becoming neuromuscularly efficient at lousy form, learning to stabilize the load with faulty mechanics.
For this reason, you should use the double-arm javelin press. It exposes the undesirable neuromuscular adaption. It's one thing to control a single, unstable object as every bit of neural drive can be channeled to that individual side. However, locking in two barbells overhead requires precise execution and textbook mechanics. There's no cheating the system on this one.