The most under appreciated rune on Urgot is Phase Rush. You're playing a champion who's main source of damage relies entirely on positioning, you need to be able to move around to get passive procs off. Urgot's biggest weakness is mobility, why wouldn't you want to try this? Anyone who plays Urgot knows you do ridiculous damage mid game no matter what damage rune you have.

Phase Rush works especially well vs champs that would normally easily keep you at arms length like Kayle, GP, Vlad etc or champs you'll normally be 100% dead if they catch you i.e Darius. You can run it in any matchup since it is a great rune to have in teamfights or to escape ganks, but its not going to feel good in lane vs champions like Renekton who has point and click hard CC and no skillshots.