Inspired by Gremrod's great example I also started an adword campaign for Perpetuum on $3 a day.
Let me give you an update what I am experimenting with.
These are the ads that I am rotating:
Perpetuum - Sandbox MMO
Have you got what it takes?
15 Days Free Trail
link: perpetuum-online.com
Perpetuum - Sandbox MMO
Persistent sandbox universe
Player driven economy
link: perpetuum-online.com
(and for both the same but with Sci-fi instead of Sandbox in the title and description)
Getting a 1.20% CTR on search placements and 0.09% for display ads.
However the display network volume is 28x time the search volume.
My top keywords:
sandbox mmo
sandbox mmorpg
mech mmorpg
mech mmo
free new mmorpg games
new free mmorpg
mmo rpg game
robot mmo
sci fi mmo
robot mmorpg
Also tried many other keyword combinations, including the ones provided by Gremrod; but most got horrible quality.
As for the landing page I am using the Perpetuum homepage, lacking an affiliate program I got no way to measure the impact and conversion rate that has.
Please give me your suggestions for further improvements!