I use "rip off" affectionately here, but when you write games, you will inevitably have the question of what games inspired a game you wrote. So I thought I would make the canonical list (as far as I remember it anyways). 

This is using a fairly narrow definition. Five Parsecs as a "vibe" is inspired by everything I like in scifi, so that doesn't really count, but Rogue Hammer is obviously meant to be Rogue Trader, so that counts. 

With rules, I am counting it if the idea for a rule or concept came directly from another game. 

The list is probably incomplete but I will expand it when I can.

Fast And Dirty

Morale checks on multiple dice came from White Wolf's RPG dice mechanic.

Suppression, wounded and confidence levels are in the game because they were in Stargrunt 2.

Five Men in Normandy

The campaign style was based pretty heavily on Necromunda.

Some of the feel of play was inspired by Nuts but I don't think any mechanic is specifically based on it.

Trench Storm

Somewhat based on Space Marine 2nd edition (and really NetEpic at the time)

LaserStorm

Heavily based on Space Marine 2nd edition and NetEpic.

Rogue Hammer

Inspired by Rogue Trader.

Renegade Scout

Mechanically based on Rogue Trader and 2nd edition 40K.

From Shako to Coalscuttle

4 stand units was inspired by a Neil Thomas game on 19th century warfare. 

Five Leagues From the Borderlands

Melee combat is heavily inspired by the roleplaying game Eon and the Inquisitor miniatures game. 

Squad Hammer

The idea of "flexible" hit roll numbers was inspired by writings on Matrix gaming methods.

War Story

The concept was based on Matrix gaming methods and Kriegspiel methods.  

MISCONCEPTIONS

These are questions or misconceptions I have gotten about where I got things from. I don't mind these but I thought it'd be fun to clarify things. This can also be updated over time.

The FAD morale check was taken from Chain Reaction.

Negative. FAD dates back to when I had just moved to the United States (though it hit the public around the same time as Chain Reaction) and as noted above was inspired by White Wolf RPGs.

FiveCore was inspired by Squad Leader

Negative. I did not actually play Squad Leader or ASL until I was a fair bit older and living in Oregon.