I remember 2 slots that I haven't found anywhere yet.
-the first one had a top feature game with 5 rols positioned in a cross, something like this O O
O
O O
-the second one had a feature with an extra rol at the left that would spin but you could also spin it an extra time(costs like 10 points extra) if a special button was pushed.
So if you saw the 2nd and 3rd (there was also a 4th) were matching but the 1st wasn't, you could give it an extra spin for an extra chance.
The rolls were positioned like this: O O O O
O O O
O O
O
So the 1st rol had 1 symbol, the 2nd 2, etc.