Lovely game.
How about a few tricks?
4 x Shields + Persuedatron(?Spelling) = Money, especially on "Eliminate agents".
4 x Shields for any thievery.
Flame-thrower is fun for ambush, especially when you have three snipers to protect.
I have to turn off my accellerator card in order to complete that level where the scientist has military gaurd. (The guards seem to kill her every time on an 030...).
Run DeliTracker and leave it playing before running the game (current song will play(ish)).
Having a fair spread of most weapons across the team seems not only logical, but works. A medic is useful, as is someone with ID.
Never forget how many soldiers you can have set up ready.
Time runs faster in the game, so if you complete a mission too-quickly, maybe go get something to eat before pressing space (minimise research funding, and you need a break every now-and-again, anyway).
Probably lots I've forgotten, and noone needs to repeat the cheats(?Google).
benJamin