i use mostly blizzard stock UI, with addons below

skada - use to show dispells, healing and overhealing
holy power bar - paladin addon
omnicc - showing cooldown in action bar icons, works with #tooltip macro
Gathermate2 - own gathering data, smaller memory footprint
dues vox encounter/ bigwigs - enable only during raids
grid/ grid 2 - multi-purpose whack-a-mole heal box

other than mentioned above:

clcret/ clcprot - maintained own customized version last time (lua is a b!tch!!!). stop patching them
gladius - pvp use. currently retired from arena