Same here.

On my Dunmer Nightblade, Lvl 11. I snuck up behind him with dual Iron Daggers, and did two sneak dual power attacks in a row, and he dropped dead. This was on Master.
On my Nord Warrior, Lvl 13. I kept shooting him with arrows and when he'd get near, i'd run around a cliff and up on it, making him have to chase me, then when he got close i'd jump back down. Rinse and repeat. I did die though when all of a sudden 3 Thugs showed up when i was fighting the Giant, and between all of them they got me. I had to reload, and then let the Giant take care of the Thugs for me.

In my first attempt at killing one, I got one shotted by the giant outside of whiterun at lvl 6. Came back at lvl 24 and gave the same giant an arrow in the head for vengeance. That was the first time I killed a giant.

Lv 1, took it on with my fist as a Kajiit.

Around 20 I think, for a quest given by Avenicci.

Arrows, lots of arrows. To note, I don't use enchanted items.
I felt that I had accomplished something, but I felt bad for the giant.

Right out of Helgen :

Made the giant kill krosis, then finished off the gaint with fists claws; there much profit to be had.

I don't remember my first fight right now, but I sure as hell remember my last one:

Just cast a few "Fury" spells, and a giant and three Mamoths got into a grand fight, and I wait a while and then I kill the last mamoth with archery.

Was fun.

great thing to do - Giant camp fairly close to the ruined castle staffed by imperials (western outskirts of Whiterun). Cause some havoc and run to the castle = eipic battle between giants, mammoths and soldiers, with me on top of the ramparts firing my bow like a wimp!

Same here, cleared out the moon forge for an quest, saw some mammoths and needed one for quest so I shoot at one, run into one building and was shooting at two mammoths and a giant for a long time. One of them had 20 iron arrows

I managed to avoid Giants until I took a quest which involved killing one, I was around level 50-55 ish. It wasn't my proudest moment, quite saddening really.

YES

Around level 4 or 5 I think. I spammed two giants with arrows from the other side of a river until they died. Kind of sad that giants can't figure out how to cross a bit of water.

Level two after I accidentally provoked one. You can easily outrun a giant unarmoured, so I just steered clear of its swipes and cast spells at it until it fell. Got some help from a Stormcloak patrol too.

Around lvl 15. Critical start with a bow and just kept running in circle and shooting. It was not one of those heroic victories T.T

around lvl 12, with bow, dual axes and a follower on master level

felt really good, and I needed a mammoth tusk, so useful too