'Knight and Day'
Craft a Celestial Stone
'This isn't even my final form!'
Craft a Moon Shell
'The B #s'
Use 'The Axe' whilst a music box is playing
'Til death do us part'
Kill a boss when you're dead
'You may now eat the wife'
Kill 'The Groom'
'Hero of Camelot'
Slay a Hardmode boss with 'Excalibur'
'Miss Click'
Kill an NPC with explosives
'Tactical Retreat'
Die by drowning during a boss fight
'But what will I spend on shoes?!'
Find a 'Coin Gun'
'Pretty Pretty Princess'
Wear the full 'Princess' outfit (Either set)
'Pretty Deadly Princess'
Whilst wearing the 'Princess' outfit, kill a Hardmode boss
'I did all that and all I got was this lousy key?!'
Defeat the Dungeon Guardian
'It was I who got the last Oink!'
Defeat Duke Fishron after using the 'Pigron' mount during the fight
EDIT: Here's some more!
'Your blade, it did not cut deep enough!'
Get killed by a boss when it is on low HP (less than 50)
'Hyaaaaaaaaaah!'
Break 200 pots
'Our Lord and Saviour, Cthulu'
Defeat the 'Eye of Cthulu' and 'Brain of Cthulu' in under 30 seconds each
'Early bird gets the worm...s'
Defeat the 'Eater of Worlds' in under 30 seconds, and 'The Destroyer' in under 1 minute
'All hands on deck'
Defeat 'Skeletron' in under 30 seconds, and 'Skeletron Prime' in under 1 minute
'Eye eye, captain!'
Defeat the 'Wall of Flesh' in under 30 seconds, and 'The Twins' in under 1 minute
'King of the Jungle, Tarzan'
Defeat 'Plantera' and the 'Golem' in under 1 minute each
'Bacon for Days'
Defeat 'Duke Fishron' in under 1 minute and 30 seconds
'The stars are aligning'
Defeat the lunar boss in under 2 minutes (These all can be adjusted, especially this one!)
That was a lot, hope some of them sound good!