From the top of my head..

MacPaint earlier than 2.0

MacWrite earlier than 5.0

MacDraw earlier than II

MacProject earlier than II

Word 1.0

Multiplan

Chart

Excel 1.0?

Some early public domain games...most written before 1988 should work (I know Klondike will work on a 128K if you have an early version)

Mac OS earlier than 3.3

MacVegas (good card game set...I have it and know it will work on a 128K)

Sargon (early versions...it's a chess game)

A ton more games I'm not aware of

A bunch of terminal type programs

FileMaker from the pre-Claris days?