Everyone's list is different, but here are the ones that get the most use for me:

Ffupdater

Fennec

Mull

Jerboa

Timer

Alarm Klock

Simple Apps suite- Calendar, Dialer, Contacts, Gallery, Calculator-

QKSMS

OSMAnd

Material Files

Quick Weather

VLC

Vanilla Music

Puzzles SGT

Shattered Pixel Dungeon

Gurgle