The plugins could be effects or virtual instruments. Some of my favorites are:

Sonarworks Reference 4
VocALign Project 3
iZotope Tonal Balance Control 2
Waves Vocal Rider
Addictive Drums 2
Metric Halo ChannelStrip 3
Valhalla VintageVerb
Melodyne
Sylenth1
Klanghelm DC8C 3

Instruments/synths:
Omnisphere
A***og Lab 4

Effects:
Valhala Vintage Reverb
iZotope vinyl
Waves stuff like L3-LL, S1 Imager, J37, etc.
Soundtoys EffectRack

Serato Sample everything

Harmony engine
Little alter boy

I used to insert Harmony Engine on real harmonies that I actually sang. It made vocals sound absolutely massive.

battery, fm8, kontakt

strictly use tal-u-no deluxe

insane how well it replicates that old juno sound

Soothe 2

Instruments/Synths:

Pigments
Battery 4
Arturia synth collection
Serum

Effects:
Valhala Vintage Reverb/plate/room/shimmer/spacemodulator/delay
Decimort2
CLA Vocals (best plugin for vocals)
RC -20 Retro Color

the waves doubler plugins are f***ing fueeeego for background vocals

Cableguys Bundle
Antares Autotune
Waves in general but stg do NOT get their OVox s***
Soundtoys EffectRack

Recently copped a ju-06a been recreating some of my fav presets from that plugin on it

decapitator
panman
uad dimension d
uad voice of god
uad ampex atr
lexicon 224 reverb
s1 imager
uad tube tech clb1
uad la2a, 1176 etc

uad the goat