Slogans are only worth having if they're really memorable - if they stick in someones mind and stay there, so that the next time they need the services you offer they immediately remember you.
For example - a scaffolding company near me has the slogan "Satisfaction Guaranteed With Every Erection" - being a little immature, I thought that was hilarious & never forgot it, and if I ever need scaffolding I'll prob give them a call first!