Showing some of the rarest and/or most interesting items I've collected since I started playing in early 2005.

Timestamps in case you want to skip around:
1:22 Tabard of the Protector
2:16 Tabard of the Argent Dawn
3:12 Bonescythe Armor
3:49 Seal of Ascension
5:06 Eternal Quintessence
6:47 Drakefire Amulet
7:56 Royal Seal of Eldre'Thalas
8:53 Old Enchanting Librams
9:59 Competitor's Tabard
10:16 Spirit of Competition
10:39 Agent of Nozdormu
11:20 Shard of the Fallen Star
13:18 Barov Peasant Caller
14:07 Dartol's Rod of Transformation
15:01 Thieves' Tools & Certificate of Thievery
15:47 Sawbones Shirt
16:24 Sleeveless T-Shirt
17:08 [Thunderfury, Blessed Blade of the Windseeker]
18:37 Twin Blades of Hakkari
19:34 Mail

Onyxia chain footage by ferfismc: https://www.youtube.com/watch?v=myj4g07wb88

Music from ocremix.org:

'WetGrass Inspired' [Tristram] by AmIEviL: https://www.youtube.com/watch?v=wordp9vBB38
Cataclysm Defenders of Azeroth: https://www.youtube.com/watch?v=lADU8m3qCfU
WoW Login Music: https://www.youtube.com/watch?v=eE5oaOOwInE
Link to the Past: Credits Acoustic Remix by ThunderScott & 8BitBrigadier: https://www.youtube.com/watch?v=9W0_fxDmDA8
Ironforge Music: https://www.youtube.com/watch?v=pTJbhw-6fws
'Holding my Thoughts in my Heart' Cover by Harry Murrell: https://www.youtube.com/watch?v=XFtsETk-eHI
Last Stand of the Blood Elves: https://www.youtube.com/watch?v=heCQfQai9zs