Tower-side modifiers
Unsupportive (+20%, no Heroic supports), Shortsighted (+10%, range -30%), Telescopic (-15% reward, range +30%). Telescopic is a free win for Sniper / Mage / Hyperlaser lineups.
Enemy-side modifiers
Hyper (+10%, speed +15%), Extremely Hyper (+15%, speed +40%), Double Trouble (+15%, 2x spawns), Triple Trouble (+30%, 3x spawns), Bullet Proof (+15%, HP doubled).
Reward-vs-risk math
Bullet Proof on Hard Endless triples effective enemy HP, turning wave 30 from survivable to guaranteed leak. Use the Modifier ROI tool to compute expected Tix/min before accepting.