I personally like them still alive and under constant paralysis with lingering damage.

i like to Keep them alive while i kill imperials.
i kill them sometimes just for steel arrows even though i join the stormcloaks all the time.

As quickly as possible because there's no pleasure in it like there is for Thalmor.

With a manly tear for my brother Nords.

Rebel scum.

Feed em' to the Troll under the Embassy.

I 'put them to the sword' as general Tullius would say. Usually decapitation.

The same way I kill off the Thalmor, just with ignorant humans instead of snobby elves.

"With the new DLC the most frequent way of killing them is using the new shouts. Before that though my main character takes them out every way he can and he actively hunts them down. Most frequent ways are turning them to dust with shock spells, thooming them off cliffs. beheading, and necromancy to turn their dead comrades as well as anything else against them. A particular great time is when I fast traveled with 2 dead giants then watched them tear apart the remnants of their embassy."

I've also done the zombie giants thing to Windhelm, as well s summoned Odahving on both.

For my Legionnaires I kill them quickly without anything attached. Extending their death is ineffective and wasting time. Same the other way around, when I kill Legionnaires.

I like to tie them to a boat in the burning sunshine in the middle of a lake. Then i proceed to apply honey all over the victins chest and stomach and let him/her lie there for a few hours. Soon the honey attracts insects, and they start feeding off the helpless stormcloak tied onto the boat. Eventually the insects start making a home for themselves in the victims stomach, and multiply while the larvae feed of the nutricious honey. Eventually the stromcloak rots away until only bone is left. And that my freinds, is how you deal with a stormcloak.