@Mon (Pronounced atmon) by Andre Fachat is a machine language monitor for the Commodore 64.  There are two versions in the archive, one that loads at $c000 (49152) and another at $6000 (24576).  Full documentation and source is included.

64Mon v1.03 is a machine language monitor cartridge by Handic (1983).  The program can be started with "SYS 32820" and the help screen can be accessed with the F7 key.  Here is a link to a post on the Lemon64 forum that has some further details on its features.

Elite Mon is a machine language monitor for the Commodore 64.

Hesmon 2.0 machine language monitor - cracked by The Dragons meaning they relocated it to location 36313 and slapped there name on it. Anyway, SYS36313 from basic to get into the monitor.

JamaicaMon v2.2 released 10/3/99 for the CMD SuperCPU is a machine language monitor supporting the SCPU Accelerator. Docs are included in the archive.

Megamon 64 by Mark Schultz is not only a great ML Monitor, it is also very well documented. Docs are on disk.

Micromon is an ML monitor that resides between $9000-$9fff. You can enter the monitor with "sys 36864".

Rammon $c000-$d000 by Police - Your standard maching language monitor residing at decimal 49152 (sys 49152 to start).

StringMon by John McCarthy is a machine language monitor for the Commodore 64.  As described by the author:

STRINGMON has lots of advanced options like cursor scrolling, 1541 disk memory disassembly, walking through code, sending to printer, and even a built in linker for loading 6502 object code. With the full version, you can even swap out the kernal memory on the C64 and view the full C64 memory.

Included in the archive are two version, one that loads into $d000 (49152) and another for $8000 (32768).  Also included is the source code, but you can find that and more at the Github repository for StringMon.

On this disk is Super 64 Mon by the famous Jim Butterfield. Also included is an excellent set of instructions by Richard Bradley of the Toronto Pet Users Group.

SUPERMON+64 v1.1 by Jim Butterfield is a new version of 'SUPERMON' that provides identical commands to those of the built-in ml monitor on the Commodore 128.

- Use LOAD"*",8  and NOT 8,1

The Drive / 64 Monitor is a machine language monitor for both the 1541 floppy drive and the Commodore 64.  It was written by Mike J. Henry and released by Starpoint Software in 1984.

VICMON is the nickname of the hexadecimal machine code monitor designed to enable easy debugging of machine code programs which are resident in a VIC 20 computer system. This version starts with SYS16384.

Link - Manual

Review in Commander Magazine - Issue 01 - Page 21

VICMON is the nickname of the hexadecimal machine code monitor designed to enable easy debugging of machine code programs which are resident in a VIC 20 computer system. This version starts with SYS24576.

Link - Manual

Review in Commander Magazine - Issue 01 - Page 21

Wiz-Mon by Magic Disk (January 1990 issue) is a machine language monitor for the Commodore 64.  This particular version can be loaded into various memory locations ($1000-$2000, $6000-$7000 & $c000-$d000) and has the instructions built into the program.