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One of the RPGs that I really really and really really do love is Delta Green.
In its first instance (back in 1997) Pagan Publishing created Delta Green as a campaign for a modern-era Call of Cthulhu game. It proved to be a success and so they expanded the product line, first starting with Delta Green: Countdown in 2000 and then throughout that decade.
In the game, you play as a member of the secretive Delta Green organisation and are asked to attend certain 'strange' events. As everything is covert, there are no emergency vehicles with flashing sirens or bulletproof vests with the government agency printed on the back. Your player may well come from an official agency, but what you do for the Delta Green agency is to be kept very low-key and as secretive as possible. It could be you have to provide your own equipment! There are lots of scenarios and some big campaign books which can take you global.
Delta Green has won Origins and ENnie Awards and continues to be well respected.
Back in 2011, a new partnership took over Delta Green (Arc Dream Publishing was born from this) and in 2015 they launched a successful Kickstarter to print the GM's book (known as the Handler's Guide) and the player's book (known as the Agent's Handbook), Delta Green then became a new Roleplaying Game all on its own. It took the Call of Cthulhu (BRP) ruleset and expanded upon it, just tweaking it (and in my opinion) making things better in a couple of simple ways:
The dice-rolling system for criticals and fumbles was simplified. Any double equal to or under your skill is a Critical Success, any double over your skill level is a fumble. No longer do you need to calculate both based on your skill. Another good change is lethality - basically, some weapons and monster attacks can kill you outright. When you roll damage you roll percentage dice, if it's equal to order under the lethal rating, the target is dead. If you roll over you add the dice together, which can be enough to kill the average player!
But enough with the history lesson. If Delta Green is new to you, there's a free supplement called 'Need to know' - you can find it here: https://www.drivethrurpg.com/en/product/175760/Delta-Green-Need-to-Know
However, if you want more than that, then Humble Bundle (a fantastic source of cheap RPG bundles that provide support to charities) you can find a bundle giving you 20 of the best current products (ruleset, campaigns, plus more) all available for as little as £15 (please give more) right here: https://www.humblebundle.com/books/delta-green-rpg-collection-arc-dream-books
But don't stop there, pop over to the Delta Green website and see what other great products are available.
It doesn't stop there, Delta Green is now also available on both the Roll20 and FoundryVTT's.
Let me know what you think about DG, should I calm down by fanboy for it? or bolster it more?