The main trick consists in getting one node (for warmonger) and activate all the key nodes and the planetary defence center with this only weapon. During the reboot sequence, get as many effective weapons as you can (roughly speaking, 1- thundersmack, 2- groovitron, (3- doppels, (4- zurkon) ) but 3 and 4 are not necessary at all, except for NG+, maybe...).

Choosing weapons, changing weapons (with triangle), purchasing or selling anything and "start" menu have no impacts on the in-game time (use them as much as you can for "NG+" runs !). That's why you should get nodes when sequence is rebooting and take your time to choose weapons. This information still has to be verified on "Zurgo's lair of doom" but it must be the same.

Thundersmack is really OP.

Warmonger is really OP.