Here are some riffs which i think are cool and fun to play.

Riff 1
------------------------------
------------------------------
------------------------------
----------0-------3-------3h5-
----3-------3-------5h3-------
--0---5h0-----5h0-------0-----

Riff 2 (This one is by Ritchie Blackmore)


-------------------------------------------------------------------
-------------------------------------------------------------------
-----3h0----5---3h0-----------------3h0-----5--3h0-----------------
-----3h0----5---3h0-----5--5--5--5--3h0-----5--3h0-----3--3--3--3--
------------------------5--5--5--5---------------------3--3--3--3--
-3--------3----------3-------------------3----------0--------------

Riff 3,4,5 (these are blues pieces)

Riff3
----------2--------------0------------------------------------------2
--------0---0----------2---2----------------------------------------0
------2-------2------0------0--------4-------3-------2--------------2
----1--------------2------------------------------------------------1
--2--------------0----------------5----5--4----4--3-----3--2--0--1--2
-------------------------------0---------------------------0---------

Riff4
-----0--------0--------0--------0-----0-------------------------
--5-----5--3-----3--2-----2--1-----1--0---2---3---4-------------
------------------------------------------2---3---4-------------
----------------------------------------------------------------
----------------------------------------------------------------
----------------------------------------------------------------

Riff5(palm mute all of this)
---------------------------------------------
-----------------------------------------5---
-----------------------------------------4---
---------------------------------------------
-2---2-4---4-2---2-4---4--5---2-4---2--------
-0---0-0---0-0---0-0---0--0---0-0---0--------

--------------------------------------2------
--------------------------------------0------
--------------------------------------2------
--------------------------------------1------
-2---2-4---4-2---2-4---4--5---0---1---2------
-0---0-0---0-0---0-0---0--0------------------