Here’s a Maxi Loop puzzle. It probably doesn’t quite deserve to be called “hard” due to the small size, but the intended logic should qualify.
EDIT: This didn’t quite work out intended, see Puzzle 91b instead.
Rules Draw a single closed loop that connects cell centres horizontally and vertically, visiting every cell. Clues indicate the length of the longest loop segment in that room.
Here’s a Horse Snake puzzle.
Rules Shade some cells to form a snake which does not touch itself, not even diagonally. Head and tail are given. Clues indicate the number of shaded cells that are a knight’s step away from the clue. Clues can’t be shaded.
(I’m pretty sure you can drop the “can’t be shaded” part and solve this as a “transparent” Horse Snake.)
We’re currently running a review series for the 2016 24 Hours of Budapest on croco-puzzle. I made this Anti-Knight Kakuro, a type which occurred in Tawan‘s set. It turned out to be a bit too hard.
Rules Solve as a standard Kakuro. In addition, equal digits must not be a knight’s step away.
One Tom-tom puzzle.
Rules Fill the grid with digits 1-7, so that no digit repeats within a row or a column. (Digits may repeat within rooms.) Clues indicate the result of applying a basic operation (addition, subtraction, multiplication, division) to the digits within that room, starting with the largest digit.
Or see the instruction booklet.
Here’s a Doubleback puzzle that’s not going to be on the upcoming Polish puzzle qualifiers. The tournament takes place at 12 CET on Sunday and is open to international solvers: competition page, instructions.
Here’s an Angle Loop puzzle. As seen for instance on this weekend’s Toketa? Selection contest that you should all take part in.
Most of you have probably hear the sad news: Florian Kirch passed away last week. I can’t claim to have known him well; a little better after preparing for and competing at the WPC this year with him. That was a great experience, I’m glad I had the opportunity. The whole thing is quite a shock, more so since he seemed full of plans: He’s behind the first German youth sudoku championship that is being held this year, and was actively working towards a WPC hosted in Germany, besides a variety of activities in other fields.
If you’d like to solve some of the puzzles he constructed, I’ve collected what I was able to find. I’d be happy to extend the list. The 2015 Logic Masters certainly stands out, my favourite of his rounds there being “Vorsicht klebrig”, a set of Tapa, Fillomino and Slitherlink puzzles that had to be matched to normal, cylindrical and Klein bottle topologies.
I’ll close by reposting a puzzle dedicated to Florian’s memory that I first published here on the portal.
Rules Glue the grid to form a Klein bottle, by identifying one pair of opposing edges directly, the other pair after flipping. Then solve as an ordinary Tapa.
Here’s a practice puzzle I made for the German puzzle championships, which took place end of June. The puzzle is a Summawake, a variant of Heyawake that I haven’t seen before. I believed the competition puzzle (and the type) was due to Florian Kirch. It’s actually due to Ulrich Voigt! The instruction booklet has an example. 
Rules Shade some cells, such that all unshaded cells are connected by edge, and that no two shaded cells share an edge. A horizontal or vertical stretch of unshaded cells may cross at most one area boundary. In addition, if there are any unshaded clues within an area, the number of shaded cells within that area must be equal to the sum of unshaded clues within that area.
I’ve made some star battle puzzles recently, for a series on croco-puzzle that’s starting today. Here’s one that turned out a bit hard. 3 stars.
Rules Place stars in some cells, such that each row, column and area contains exactly 3 stars. Cells with stars must not touch, not even diagonally.
I hope you enjoy these Checkered Fillominos as much as I do. This one came out clearly too hard for this year’s 24h puzzle championship in Budapest. (April 17-19, I don’t think it’s too late to join.)
EDIT Fixed an amibiguity. (Hopefully. Thanks Prasanna for finding it.)
Maybe Puzzles 