The editors of Men's Fitness reply: Try the 'lying pull-over press' - it hits numerous upper body muscles including your core, back, chest and arms, and you can be in and out of the gym in a matter of minutes.
The move is basically a pull-over followed by a chest press. Aim to do three sets of 12 to 15 reps. You can alter the move to target particular muscles if you wish:

Pecs: add 12 to 15 chest presses between the pull-overs.

Back: use an eight second descent and four second ascent during the pull-over.

Triceps: Move your hands until they're about six inches apart and do a series of close-grip chest presses.
part 1
Elbows bent 90 but not flared out to the sides. Abs and core tight. Lower back lightly arched. Feet flat.
part 2
Barbell pulled overhead in an arc. Bar positioned in line with lower pecs. Abs and core tight. Elbows bent 90. Lower backslightly arched. Feet flat.
part 3
Arms extended but elbows not locked out. Abs and core tight. Lower back arched. Feet flat.