Specials

In 1943 the third G-series pre-production aircraft was modified to test a butterfly tail.
There was a small increase in top speed but at low speeds stability was a problem.
No further tests were made.

(Source: Die Deutsche Luftfahrt, Willy Messerschmitt & AJ Press Monografie: Messerschmitt Me-109 Cz. 2)

In 1943 a F-2 airframe was tested with 4 EG RZ85 rockets in each wing.
The installation had an unfavorable effect on the flight characteristics however
and no further experiments were made.

(Source: Messerschmitt "O-Nine" Gallery)

(Source: AJ Press Monografie: Messerschmitt Me-109 Cz. 2)

Me-109 G-2 with an experimental central MG 151/20 gondola (Source: AJ Press Monografie: Messerschmitt Me-109 Cz. 2)

In 1944 a FuG 216 radar was installed in a G-6 airframe and tested as a single seat night fighter.

Messerschmitt Me-109 G-6 fitted with FuG 217. (Source: Luftwaffe at war, Nightfighters)

Messerschmitt Me-109 G-6 fitted with FuG 217. (Source: AJ Press Monografie: Messerschmitt Me-109 Cz. 2)

Messerschmitt Me-109 G-6/R6 fitted with FuG 350 Naxos. (Source: AJ Press Monografie: Messerschmitt Me-109 Cz. 2)

In 1941 a standard E-4 was fitted with skis.
In practice the normal wheeled undercarriage proved able to cope with
packed snow airfields and the skis were not necessary.

(Source: Messerschmitt "O-Nine" Gallery)

Full wheel well covers were tested on a G-series airframe.
This reduced drag but the increase in performance was not enough to justify this modification.

(Source: Messerschmitt "O-Nine" Gallery)