slashbinbash.de / Freeware Recommendations

Analysis

API Monitor
Monitors Windows API calls of running programs
OllyDbg
32-bit assembler level analysing debugger
Speccy
Retrieves tons of useful system information
Sysinternals Suite
Collection of useful troubleshooting utilities
WinDirStat
Disk usage statistics viewer and cleanup tool
Wireshark
Program for network traffic capturing and analysis

Archiver

7-Zip
File archiver with a high compression ratio

Converter

CDex
Converts music CDs to WAV, MP3, OGG and more
VirtualDub
Video capture/processing utility for AVI files

Emulation

BGB
GameBoy and GameBoy Color emulator and debugger for Windows
FCEUX
Nintendo Entertainment System (NES) and Famicom Disk System (FDS) emulator

Games

Battle for Wesnoth
Turn-based tactical strategy game with a high fantasy theme
Dwarf Fortress
Fantasy simulation
FlightGear
Realistic flight simulator
Freeciv
Remake of the original Sid Meier's Civilization
OpenArena
Clone based on the original Quake 3 Arena engine from idTech3
OpenRA
Remake of Command and Conquer: Red Alert with many improvements
OpenRCT2
Open source RollerCoaster Tycoon implementation with many improvements
OpenTTD
Open source simulation based on Transport Tycoon Deluxe
POWDER
Oldschool roguelike with simple graphics
Quake Live
Play Quake 3 Arena online
Simutrans
Transportation simulation game similar to Transportation Tycoon
Tales of Maj'Eyal
Tactical RPG roguelike
Team Fortress 2
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The Zod Engine
Remake of the game Z with multiplayer and level editor

Graphics

Alchemy
Program for creating abstract art
Blender
3D modeling program
GIMP
Image manipulation program similar to Photoshop
MagicaVoxel
8-bit voxel art editor
Paint.NET
Very basic image manipulation program similar to MS Paint
yEd
Powerful diagram editor that can be used to generate drawings of diagrams

Internet

Chrome
Google's web browser
Firefox
Alternative internet browser to Internet Explorer
HexChat
IRC client based on X-Chat
PuTTY
Telnet/SSH client
Thunderbird
Easy-to-use email client and address book
Transmission-Qt Win
Very minimal, basic BitTorrent client

Multimedia

Audacity
Audio editing and recording software
InfraRecorder
Writes CDs/DVDs (data, audio, video, images)
OBS Studio
open source software for video recording and live streaming
ScreenToGif
Screen, webcam and sketchboard recorder with an integrated editor
Sidplay2
Plays SID files (C64 music)
VirtuaNSF
Plays NSF files (NES music)
VLC
Sophisticated multimedia player

Office

MiKTeX
TeX implementation with additional tools and content, comes with the TeXworks editor
LibreOffice
Program suite similar to Microsoft Office with additional features
PDF Split and Merge
Does what the name says
TeXworks
Minimal but very reliable LaTeX editor

Programming

Code::Blocks
C/C++ development environment
Eclipse IDE
Development environment primarily for Java applications
GNU R
Free software environment for statistical computing and graphics
HxD
Powerful hex-editor and disk-editor
Notepad++
Extended Notepad with syntax highlighting, spell-check, macros and more
Visual Studio Code
Cross-platform code editor, debugger, GIT support, etc.
Visual Studio Community
Free version of Microsoft Visual Studio
WinMerge
Differencing and merging tool that can compare folders and files

Scorewriter

LilyPond
Text based music notation program

Security

Microsoft Windows Defender
-
CCleaner
System optimization, privacy and cleaning tool
Malwarebytes' Anti-Malware
Scans your computer for persistent viruses and trojans

Trackers

AdlibTracker
OPL3 FM-chip tracker
FamiTracker
NES/Famicom music tracker
GoatTracker
C64 music tracker
LittleGPTracker
Tracker based on LSDJ
MilkyTracker
Tracker based on FastTracker 2
OpenMPT
Popular tracker with VST capabilities
SchismTracker
Tracker based on ImpulseTracker
SunVox
Advanced modular tracker

Instruments/Effects

BR404
farbrausch synth
BR808
farbrausch synth
Dexed
FM synth that is closely modeled on the Yamaha DX7
PG-8X
Synth inspired by the JX-8P
Synth1
VCV Rack
Open-source virtual modular synthesizer

Virtualization

VirtualBox
Computer virtualization tool
WinCDEmu
Mounts ISO, CUE, NRG, MDS/MDF, CCD, IMG images