There are a lot of hostile effects out there, but I think the only positive effect I've ever seen in the game is the guardian defending you buff in Lockdown.

I'd love to see new buff pills that temporarily increase your attack value, the overall health of your shield, and your movement speed. Attack and speed increases already exist, but I'd like to see block value increases on some armor items, and I'd love to see block and speed increase trinkets in the game.

Also, I'd love to see a "Critical Boost" type of stat on some trinkets or maybe as bonuses on items, where you are given a positive buff when you reach 10% or have less than 1 HP for a specific period of time.

I guess while we're throwing buffs out there, I guess there should exist a debuff that removes positive buffs on the target. Trojan ATK up or Alpha Wolver aura could be stripped, perhaps additionally fire jellies could be put out and freeze jellies would have their ice removed. Some monsters could have their attacks modified to strip buffs as well.