Guild Wars 2

Have condition damages that flicker or fade intensity periodically with stacks.
Example: one stack flickered burning lasts for 2 seconds and ends with double damage.
Example 2: one stack of weakened chill lasts for 5 seconds. First second slowness is 66%, 2nd to 4th second slows to 33%, and last second is 80% slowness.

Other variations can be done also.

Condition or skill that causes two or more allies in the area of a targeted enemy to uncontrollably run towards that target and attack that target with an attack given by this skill or condition. This is a CC plus damage skill/condition. If no ally of enemy is present, npcs will spawn instead and attack target using cc abilities with damage.

Mirror CC skill that causes target(s) to uncontrollably mirror your movements and gain any conditions or boons that you have or receive. If you move forward, your target(s) do the same. If you quickly jump to the side, your target(s) mirror that. If you get launched back, so does the target(s). If you get feared, so does the target(s). Etc.

Skill or condition that applies strong damage and other actions when a target dodges. Causes faltered avoidance. Also reduces dodging distance. May also cause other dodging defects like ineffective dodging (does not prevent damage), loss of stamina, loss of dodging ability and incremental stamina loss when attempting to dodge, or excessive dodging.

Skill/boon/condition/effect that may increase or decrease health bar, stamina bar, profession mechanic bar and cause exhaustion of these limits to target or oneself after doing so.

Updated. Keeping the post renewed.

Skill/ability to switch between different heals while in combat (and the same for elites too).

Skill/ability to have two elite (or heal) skills slotted (one goes into a utility slot) at the cost of something like not being able to use the profession mechanic or maybe dodge.

A heal reclaim gauge bar that fills with each successful heal of an ally. When this heal bar is filled, different things can be done (increased power, increased healing, increase condition damage, be able to perform a skill, etc). Have to bar available for all professions so that each profession can have more heal support play. Each profession could have their own unique mechanic for the heal bar too. There could be more bars like this to support other type of gameplays (support, buffs, interrupts, cc, etc) that could use more play support.

Skill/ability to manipulate another professions mechanic related thing (like remove amounts of initiative, increase activation times of atunements, cause damage when using a shatter skill, etc). And manipulation for weapon swapping too.

Skill/ability to slot four heal skills ( three in place of utility skills) or four utility skills (one in place of elite skill).

Making it non linear in application could be problematic, doing less or more dmg before cleanse.

I only care about my dmg actally being applied…..