Ok this was an idea that I got that sounds like it'd be a great strategy. Take Garen's best move and make it unstoppable. I basically made a high damage high crit build for Garen. judgement wisely and it could be your greatest asset in a team fight. Plus with the high damage this could be a 2 move hit on some champs go from justice to demacian justice and bam! dead. Also because of this build you are not really affected by the reduced minion damage so spin away on them or in the jungle. Anyway I'll just get started on explaining myself.

My choice of runes is basically meant to make Garen survive more. Increase his Armor with glyphs and seals and use the quitenceses for health. The Marks however I increased armor penatration because if you have bulky guys on the other team you want to be able to take them out. Now some substitutes you could use are the ones that reduce cooldown because then your champ can spam justice even more.

I'm not going to go too in depth with the masteries, I did 14/16/0. Now I did this because I wanted a good balance of attack and defense. If you think that you can better go ahead this is what I've just seen work.

The skill sequence is pretty much good in my opinion. Obviously if you're having trouble surviving take some extra points in courage. The main reason I max courage last is because one this is built on justice and two decisive strike is a great way to chase or silence enemies and take down turrets since they are unaffected by justice.

The items are what help the most. Ninja Tabi to reduce the basic damage you take. Sunfire Cloak because while you are spinning you'll be in range for extra damage plus extra health and armor. Infinity Edge adds attack, crit chance, and crit damage this is a must if you do this build. Phantom Dancer x2 because this will add 60% crit chance and make you mobile making it easier to get in and use your attacks. Lastly Ghostblade because it reduces cooldowns adds armor pen and adds that last bit of crit chance for 100%. Now obviously there are some alternatives in the items. For example don't like Sunfire? Get frozen mallet or warmongs but if you do this I recommend using atma's impaler instead of ghostblade for the extra armor and damage while still keeping the crit chance.