Openings to reach endgames fast

You should probably work on not hanging material, missing simple tactics, and not following opening principles.

"... we can see from the above that players who are happy as White to play for a small edge in a queenless middlegame have a number of lines where they can achieve the sort of position they want. Even in other variations, the willingness to settle for a near-equal endgame, rather than trying to obtain an objective opening advantage, makes one's whole job of opening repertoire management very much easier. ... With his superb intuition and depth of positional understanding, [Petrosian] was accustomed to treating the opening relatively flippantly, and did not normally strive very hard to gain a theoretical advantage. ... it seems to me that for many players below master level, having a repertoire where there is minimal need to prepare could in fact be quite attractive. It must be remembered that, despite its shortcomings, Petrosian's approach proved good enough to wrest the world title out of the hands of Botvinnik, one of the best-prepared players ever. ..." - FM Steve Giddins (2003)

Possibly of interest:

How Ulf Beats Black

https://www.newinchess.com/media/wysiwyg/product_pdf/9062a.pdf

https://www.chess.com/video/player/ulf-anderssons-3-most-instructive-chess-endgames

Grandmaster Chess Strategy by Jürgen Kaufeld & Guido Kern
https://web.archive.org/web/20140708093410/http://www.chesscafe.com/text/review812.pdf

I think that Fool's Mate would be an opening that reaches the endgame quickly.

Ruy lopez exchange variation can lead to end games fast. 

Apart from what has been mentioned above (Berlin and exchange in the Ruy Lopez and the queenless openings of Ulf Andersson, especially in English and neo Grunfeld, see Lakdawala's book) there are a few other options: Philidor/Maroczy against e4 (1.e4 d6 2.d4 Nf6 3.Nc3 e5 4.dxe5 etc. resp. 1.e4 d6 2.d4 e5 3.dxe5...), not entirely sure whether the second one is called Maroczy btw. I won my best win ever against a +2100 using that Philidor queen exchange, many people have a hard time figuring out a plan in such positions. See Sergey Kasparov's book "a cunning opening for black", especially the line 1.e4 d6 2.d4 Nf6 3.Nc3 e5 4.dxe5 dxe5 5.Qxd8 Kxd8 6.Bc4 Be6 7.Bxe6 fxe6 looks horrible but is a lot of fun to play as black; if you like to provoce white into running into a wall and then slowly improving your position that is. Similarly, in the Hungarian 1.e4 e5 2.Nf3 Nc6 3.Bc4 Be7 4.d4 d6 5.dxe5 dxe5 6.Qxd8 ...) leads to similar positions. And against d4 the Old Indian/rat openings give even better chances in case white exchanges queens: 1.d4 d6 2.c4 e5 3.dxe5 dxe5 4.Qxd8 ... is very playable for black and also 1.d4 Nf6 2.c4 d6 3.Nc3 e5 4.dxe5 dxe5 5. Qxd8 .. is ok I think. Bryan Smith wrote some very nice columns on this topic https://www.chess.com/article/view/new-column---queenless-positions

Also see these posts on Mednis' "from the opening into the endgame" book: http://www.chesspub.com/cgi-bin/chess/YaBB.pl?num=1154137596

http://www.chesspub.com/cgi-bin/chess/YaBB.pl?num=1177102028

Furthermore, Lakdawala presents the Ulfie/Haberditz in his book on the Sveshnikov https://www.chess.com/forum/view/chess-openings/ulfie-a-solid-svesnikov-alternative 

although I find that sicilian 1.e4 c5 2.Nf3 Nc6 3.d4 cxd4 4.Nxd4 Nf6 5.Nc3 e5 6.Ndb5 h6!? (instead of 6. ... d6) 7.Nbd6+ Bxd6 8.Qxd6 Qe7 9.Qxe7 Kxe7 much less simple to understand then the previous position where black play d6 and e5 allowing a queens exchange. In these you typically just have to take care of e5 pawn and the d5 square (play c6 if possible) and think where to put your king (keep it central in the endgame) and then its very playable. 

If I remember well, there are also some options in the Tarrasch French, QGA, the c3 Sicilian, the Petroff but you have to check the links to see for yourself. I like the idea of 1.e4 d5 2.d3 dxe4 3.dxe4 Qxd1 against the scandinavian and the 1.e4 e5 2.Nf3 Nf6 3.Nxe5 Nxe4 lines as black (which is more or less playable for us amateurs if you know some lines) just make people think they are going to refute the opening but that's more psychology and warfare than objective chess I guess  

I guess the Berlin is the most serious queenless opening, John Cox' book The Berlin Wall does a really good job explaining the endgame thinking (which pieces do you have to keep on the board?) ; if you want to spend studying hundreds of pages on a variation you will see 1 in every 10 or 20 games at amateur level that is