To bring up the cheat console, press and hold the CTRL and ~ (TILDE, THE KEY ABOVE TAB) keys until the prompt appears. From there, you can enter the codes indicated below for the corresponding effects.

Code	Effect
Annex [Nation Tag]	Annex nation indicated.
instantproduction	Instant Production.
manpower	Extra Manpower.
pp	Extra Political Power.
research [slot number]	Complete Research for specified slot (or enter 'all')
unity [#]	Increase Unity.
xp	Added Infantry, Naval, and Air experience.
yesman	Agreeable Diplomats.