Hmm, just off the top of my head...
(Well, actually, browsing Touhou Wiki)
EoSD: Rainbow Sign "Wind Chime of Colorful Raibow" always was a favourite of mine for some reason, Heaven's Punishment "Star of David" was neat to me as a new Touhou player (Still prefer it over Young Demon Lord), and Taboo "Kagome, Kagome"
PCB: Great Funeral Concert "Ghostly Wheel Concerto Grosso" was the first noticable spellcard to me, Hell Realm Sword "200 Yojana in 1 Slash" is another favourite (Although ARGH), and "Resurrection Butterfly -__% Reflowering-" of course.
IN: Where Danmaku starts to REALLY get interesting to me. Pseudo-History "The Legend of Gensokyo", Border World "Hakurei Danmaku Bounded Field", Black Magic "Event Horizon", Lunatic Gaze "Illusion Seeker", Lunar Eyes "Remote Rabbit", Mind of God "Omoikane's Brain", Esoterica "Astronomical Entombing", Impossible Request "Hourai Barrage -Rainbow Danmaku-", Reincarnation "Returning-Bridge Ichijo", Forgiveness "Honest Man's Death", "Blazing Star", "Deflation World", and "Profound Danmaku Bounded Field -Phantasm, Form and Shadow-" @_@
MoF: Flood "Ooze Flooding", Sea Opening "The Day the Sea Split", "Mountain of Faith"/"Virtue of Wind God", Native God "Long-Arm and Long-Leg"
SA: My other favourite Danmaku. Envy "Green-Eyed Invisible Monster", Malice Sign "Day 7 of the Midnight Anathema Ritual", Four Devas Arcanum "Knock Out In Three Steps", Recollection "Terrifying Hypnotism", Malicious Spirit "Spleen Eater", Response "Youkai Polygraph"