I wouldn't really call it unnecessary, but..
TellMeWhen - Configured to perfection to show exactly what I need it to show for my 3 90's so I know exactly what I need it to show when I need it. Does for me what I used to use 3 addons for (specific buffs, debuff duration on target, cd tracking).
ErrorFilter. I am spammy when it comes to brutalizing my rotation, and the lack of red letters on my screen was honestly a godsend. Thank you, ErrorFilter.
arkinventory
Align. Even after completing a UI I keep it installed just in case I need it to relocate something. Not like it takes any memory, but still. TimeToDie as well, although while its largely a control freak thing it can be situationally useful.
SLDT + Friend/Guild/Stats addon..
Used it a while back and never went for something else and when friends/guild module didnt work it made me a sad panda.
Hooray for fan support.
Aaah Align same for me, keep changing stuff around and align makes it all prettier when i move stuff.
Recount
Most have
Align.
/10chars