how about this:
revenge mode. after completing the main game, you have all the aztec equipment and have to fly twice as far to beat the crap out of that guy that dissed you at the end of the campaign.
and you only get 1 shot at it.
get a heli, toggled rocket, bobsled and something that goes BOOM! you get whirlybird and then all of a sudden BAM! you can go 12x further.
Also dont buy anything in bonus shop til after you get aztec catalog.
it wins.
wow i got first blood, cold killer, blood thirsty, mass murderer, big winner, winning streak, team captain, god gun, nail gun & shell gun, then i realised there was a campaign.